reseted all my users passwords, over 2000
I assume you were never able to log in after upgrading.
I had the same problem when I upgraded from 18.104.22.168 to 1.9.4 RC1. I tried it several times and would get a failure error everytime I tried logging in. I gave up and upgraded to 1.9.3 which worked fine.
Today I tried upgrading from version 1.9.3 to 1.9.4 and I get the same login errors.
There is definately something wrong with the upgrade, or we need more information on the web.config changes.
I started with the recommended web.config file and then changed the SHA1 to MD5 since that's what my old file was using. That didn't help any. I then compared provider add lines and copied over the older attributes like hashHex and hashCase and I changed requiresUniqueEmail to false to match the older web.config file. That didn't help either, I still got the error. I have reverted back to v1.9.3.