Go to the section – WP-Members FAQs – link below and scroll to he bottom and read
‘Use passwords are invalid? What is wrong?’
https://rocketgeek.com/plugins/wp-members/users-guide/faqs/
I did the following and now the plugin appears to be working on my site. I am hoping is will be a permanent fix but it is too soon to tell.
1. In your dashboard go to ‘Settings>General’ and make sure ‘Anyone can register is UNCHECKED.
2. In the WP-Members Options, I UNCHECKED the ‘Hide Registration’ box.
3. I read on line that sometimes caching pages for plugins that force login to the front end like WP-Members does can cause a problem.
I use WP Super Cache so in ?he WP-Super Cach Settings>Advanced settings I added the strings for the WP-Member pages that force those pages not to be cached,ex. /register/, /members-area/, /sign-in/
4. If you are using something other than the recaptcha that is suggested in the WP-member settings, you may have to deactivate ?hat plugin as it may cause a conflict.
I did those 4 things and now I can login via the WP-Members login. Like I said, it is too soon to tell if it permanently fixes the problem.
One other thing – I also installed Disable XML-RPC last night when I was making the above changes and I do not know if that had anything to do with the fix.