You will need to post an actual error message, not paraphrasing.
I am
guessing that you are using Gmail and you need to
enable less secure apps.
For the record, Google is lying about them being less secure just because they don't use Google's particular brand of security.
There are many respected applications that Google claims are "less secure", calibre is one of them.
...
Last I checked, Gmail lies and says you have an invalid password even when "less secure apps" is the real problem.