Facebook buttom in SCLogin sometimes doesn´t work

By not working, what do you mean? Is there an error message, is the page blank, are you logged in but just have to force a refresh to see that you're logged in? Clearing the browser cache by ctrl-f5 - are you doing this before you attempt to log in via FB or after?

Please try temporarily disabling the System Cache plugin, any caching options in Global Configuration area, or any other plugins for caching such as JotCache to see if this helps.

My suspicion then is that the Perfect Facebook Like Box Sidebar Module was using the deprecated Facebook javascript library all.js. JFBConnect uses the recommended sdk.js as the older library has been deprecated and not recommended for use for over a year now. When both are included on the site, login functionality (or other FB functionality) is flaky/doesn't work. It's possible that the previous version of JFBConnect that you were using was still on the old library and thus worked with the module still.

-Melissa

Not a problem. Let us know if you run into any other issues.

The Login / Register at the top of our site is just the SCLogin module. We have it placed in a module position that displays in the top right of the page and have the display mode set to display "Text Links" instead of buttons. That's it!

I hope that helps, but if you need anything else, just let me know.

Thanks,
Alex