Happen to have 1password back in 2015 and now cannot sync because I cannot remember old password

this solves my problem!

That's great to hear @KRPX! Please keep us posted in case you hit any obstacle :)

@ag_anan this solves my problem! I need to delete first from my mac

@KRPX:

Can you try these instructions to erase your existing 1Password data in iCloud and see if you can then setup sync again?

https://support.1password.com/cs/icloud-troubleshooting/#step-5-reset-icloud-data-in-1password

Hi, I would like to Erase iCloud data. But it doesn't allow. I saw only merge option which required old password.

@KRPX:

I am sorry to hear about this. For your privacy and security, your Master Password is not stored anywhere, only you know it. This means that it is not possible to recover it unless you are a member of a Families or Business accounts. If you are trying to configure an old standalone vault, I recommend reading this article to try and recover your Master Password:

https://support.1password.com/forgot-master-password/

how about I just want to back up new 1password to icloud instead? but it does not allow me to do so. It only asks me to merge option.

You should see an option named Erase iCloud Data under 1Password Settings > Advanced, if you are absolutely sure you will not be able to remember this Master Password, and you would like to start with a new empty vault.

how about I just want to back up new 1password to icloud instead? but it does not allow me to do so. It only asks me to merge option.

Is there anything I can do?
If it is a local vault, I think this vault is lost if you can't remember the password you protected this vault with...