Can't Log In to SuiteCRM using 7.9.8 with a known good username and password.
Problem appears to be from theme updates including SuiteP, SuitePImproved, and SuiteP_ElDraft and lies in the login.tpl file of the theme located /themes/tpls/login.tpl
Remove the login.tpl file, or in my case, I simply changed the name to login1.tpl (I was in a hurry, or I would have changed it to login-doesn't-work.tpl
According to the forums -> https://suitecrm.com/forum/installation-upgrade-help/17082-can-t-login-with-username-password-on-7-9-8
There's an update to SuiteP that addresses this issue, and I thought it was taken care of, albeit after a day or two of working, the issue simply came back. I may try copying and pasting the latest SuiteP theme update for 7.9.8 into SuiteP-ElDraft (the theme I edited and using as of this writing).