Unable to use admin panel

[Molione]

Hello! This is my forum, just moved over from Icyboards. http://livingthedream.sunberryrp.com/

I've just finished moving in the old database, and upgraded the forum successfully. However, when I log into the admin panel, I can't get past the index. If I try to navigate, it takes me back to the login page. Entering my credentials again just tells me it is an 'invalid administration session' and won't let me access the module, even though my username/password lets me log into the forum and log into the ACP Index.

I've skimmed a lot of topics and tried a few things, but I'm having no luck. (Something likely seems to be plugins? But it won't let me get into the admin panel to disable those at this point so I'm not sure how much it would help. I have cleared my cookies on this browser, no luck.)

I would appreciate any suggestions or assistance! Thank you for your time in advance! :]

[.m.]

basically you have to use the new url of your forum for the board url
& also change cookie settings according to the new url. These changes
can be first done in settings.php file (in inc folder) AND then at the
admin panel of your forum.

settings.php file can contain below to suit your new forum url

$settings['bburl'] = "http://livingthedream.sunberryrp.com";

$settings['cookiedomain'] = "sunberryrp.com";
$settings['cookiepath'] = "/";

more details => faq: login problems

above referred settings should be also changed again at forum admin panel

forum admin panel >> configuration >> site details

[Molione]

Thank you so so much for laying this out! I really appreciate the detailed approach. The problem seems to be all fixed up now. Thank you again!! <3