Sorry – this came in too late for me last night – I had already gone to bed. Normally, Steve is able to take over in the US bur just last night he was away.
Give me the exact name and WordPress url of this plugin and I will download and activate it on my test site to see if I get any cinflict

The Plugin is “Login With Ajax”

https://wordpress.org/plugins/login-with-Ajax/

I have a mad desire to everithing works.Thanks so much!!! : – D

1. I experience no actual problem running this plugin as a widget in the sidebar alongside Simple:Press. Nothing, as such, gets messed or goes actually wrong.
2. The plugin DOES produce an error in the script console when the login action takes place without a page reload. The message is ‘Syntax error, unrecognized expression’ and is triggered in jQuery. It would be useful if you contact the authors and ask them to look into this and, hopefully, fix it up.
3. IF you use the full AJAX version with no page reload then you do have to remember that the loaded and displayed page was constructed and rendered for the user NOT being logged in. So there will be things that do not work as a logged in user might expect. This is not forum specific but will apply to anything that displays differently for logged in/not logged in users.

The last point really does make using AJAX to log in rather pointless and potentially confusing of course. There is absolutely nothing you can do to rectify that.

The author of my WP theme has found the problem, they just did not have to do with the subject of WP or Login With Ajax.

Your captcha plugin for SimplePress makes a conflict with the jQuery. In Chrome, “inspect element”, “console” appeared this message:

“Uncaught TypeError: jQuery(…).captcha is not a function
VM160:1 ‘webkitIDBDatabase’ is deprecated. Please use ‘IDBDatabase’ instead.”

Clicking on the error, it took me to a section where data appeared the captcha plugin of SimplePress (scissors, notes, etc.). I uninstalled this plugin and I’ve erased, and again everything worked.

unable to duplicate the issue you refer too…  does this ajax login plugin use its own version of jquery (or jquery ui)???  we simply use the version that comes with wp…