Hello fellow gamers, I had the same issue and found a 100% way to fix it.
I had previously taken an opal, and while loading a previous gamesave the opal was not there, the autosave fonction repaced the save where I had picked up the Opal with the earlier one where I hadn't.
I figured out it is because Opals are recorded on your Ubisoft account, and once picked up, will not reappear on earlier gamesaves.
So the solution that works is a bit annoying but takes about 10 minutes if you're efficient.
You have to create a new ubisoft account with another email.
Then delete your Ubisoft account on the website, don't worry you will be able to reactivate that account before the next day since Ubisoft sends you an email to reactivate account if you wish.
When you open the game, register to the new "fake" account and open your save. You can then pick up the Opal, do a quick save. After that delete the newly made "fake" account on the Ubisoft website, reactivate your real ubisoft account with the email you recieved, relaunch the game and log in to Ubisoft with your account. All fixed ! Good luck !

@chakra

100 % Opal previously collected solution on PS4

Hello fellow gamers, I had the same issue and found a 100% way to fix it.
I had previously taken an opal, and while loading a previous gamesave the opal was not there, the autosave fonction repaced the save where I had picked up the Opal with the earlier one where I hadn't.
I figured out it is because Opals are recorded on your Ubisoft account, and once picked up, will not reappear on earlier gamesaves.
So the solution that works is a bit annoying but takes about 10 minutes if you're efficient.
You have to create a new ubisoft account with another email.
Then delete your Ubisoft account on the website, don't worry you will be able to reactivate that account before the next day since Ubisoft sends you an email to reactivate account if you wish.
When you open the game, register to the new "fake" account and open your save. You can then pick up the Opal, do a quick save. After that delete the newly made "fake" account on the Ubisoft website, reactivate your real ubisoft account with the email you recieved, relaunch the game and log in to Ubisoft with your account. All fixed ! Good luck !

You need to delete your real account and create another one on the Ubisoft site.
Quit the game, when you'll open it, the game will ask you to register to a Ubisoft account in order to play, that's when you register to the newly created account.
Then pick up all the opals you need since the account has no registered opals on it.
Save your game, quit the game. delete the fake account and reactivate the real one.
When you open the game again, register to your real account.
I did it twice for two opals missing and worked perfectly, let me know if you have any questions and good luck !

Hi, I'm on PS4., I guess this solution doesn't work on PC...
Don't worry, you won't delete your account, only temporarily to get the opal, then you reactivate it 15 minutes later once done! Otherwise I think Ubisoft will probably patch this soon. Good luck to all and enjoy!

You need to delete your real account and create another one on the Ubisoft site.
Quit the game, when you'll open it, the game will ask you to register to a Ubisoft account in order to play, that's when you register to the newly created account.
Then pick up all the opals you need since the account has no registered opals on it.
Save your game, quit the game. delete the fake account and reactivate the real one.
When you open the game again, register to your real account.
I did it twice for two opals missing and worked perfectly, let me know if you have any questions and good luck !

Here is the solution to the Opal bug https://discussions.ubisoft.com/topic/77724/assassin-s-creed-valhalla-opal-bug/6?lang=en-US

Hello fellow gamers, I had the same issue and found a 100% way to fix it.
I had previously taken an opal, and while loading a previous gamesave the opal was not there, the autosave fonction repaced the save where I had picked up the Opal with the earlier one where I hadn't.
I figured out it is because Opals are recorded on your Ubisoft account, and once picked up, will not reappear on earlier gamesaves.
So the solution that works is a bit annoying but takes about 10 minutes if you're efficient.
You have to create a new ubisoft account with another email.
Then delete your Ubisoft account on the website, don't worry you will be able to reactivate that account before the next day since Ubisoft sends you an email to reactivate account if you wish.
When you open the game, register to the new "fake" account and open your save. You can then pick up the Opal, do a quick save. After that delete the newly made "fake" account on the Ubisoft website, reactivate your real ubisoft account with the email you recieved, relaunch the game and log in to Ubisoft with your account. All fixed ! Good luck !

Hello fellow gamers, I had the same issue and found a 100% way to fix it.
I had previously taken an opal, and while loading a previous gamesave the opal was not there, the autosave fonction repaced the save where I had picked up the Opal with the earlier one where I hadn't.
I figured out it is because Opals are recorded on your Ubisoft account, and once picked up, will not reappear on earlier gamesaves.
So the solution that works is a bit annoying but takes about 10 minutes if you're efficient.
You have to create a new ubisoft account with another email.
Then delete your Ubisoft account on the website, don't worry you will be able to reactivate that account before the next day since Ubisoft sends you an email to reactivate account if you wish.
When you open the game, register to the new "fake" account and open your save. You can then pick up the Opal, do a quick save. After that delete the newly made "fake" account on the Ubisoft website, reactivate your real ubisoft account with the email you recieved, relaunch the game and log in to Ubisoft with your account. All fixed ! Good luck !