Add-on that was "Preliminary reviewed" still could not be installed

after adding and getting the status as “Preliminary reviewed” the browser still throws “firefox has prevented this site from installing an unverified add-on”

could you please help us understand why this is happening and how to troubleshoot it?

UUID:
&
UUID:

Hi, what version of Firefox are you using?
And are you installing the add-on from the Add-ons Manager or via some other method?

Did you re-download the add-on file after it has been signed?

Thank you, TheOne for pointing to the right direction.
Redownloading the unlisted signed XPI was however not a easy task. For others I’ll just put 3 steps right here, might be someone will find it useful: