Typically, a 535-5.7.8 error indicates that the password used while the inbox was connecting isn´t correct. This error typically occurs when you change the password from your email account, change the permissions, disable 2FA, or delete the app password.

To fix this issue, you would need to locate your app password for the Warmup Inbox app in this particular Google account first.

Here is an article on how to locate your app password:

https://help.warmupinbox.com/en/articles/4934806-configure-for-google-workplace-with-two-factor-authentication-2fa?location=conversation

Once you see the app password, please delete it and create a new one. Then this new app password you can copy-paste in the Warmup Inbox.

Please click on the affected inbox - settings - connection and paste it into the SMTP and IMAP password fields and hit save.

Once done, you should be able to unpause your inbox without issues.