It's not working for me. I've linked my existing Fastmail and 1P accounts. I've tried my MacBook with Safari and my iPad. Both have been updated to the latest version of 1P
At https://omny.info/register I can't get it to offer me a masked password.
Thanks for letting us know about you running into some issues. I've split your conversation off into a new thread so we can make sure conversations are staying focused.
Would you mind trying this set of steps for me? --
After signing in to 1Password again to confirm the integration, verify that your Fastmail email address is shown in the Integration directory again: https://my.1password.com/integrations/active
Please let me know if after doing these steps you're able to see "Create masked email" on https://omny.info/register