You could try this......
attachment (below) show what I added in red
goto : src > XF > Service > Upgrade > Checker.php - add return true; after $checkData = [ ]; in function check
you will need to add the following lines
return true;
.
.
.
return $upgradeCheck;
}
and save it.
So i test this on localhost without internet connection and works. I plug-in internet connection reboot computer so I now have internet connection.
I added the following lines BEFORE i install xf 2.2.15 - and then do a clean install of Xf 2.2.15
and it seem to have worked.
Test 1. I did not test on live web hosting but tested with internet on localhost and 1st install without added lines and got cURL error.
Test 2. I connected internet - added the lines explained above did a 2nd clean install xf 2.2.15 with added lines and NO cURL error.
Hope I have explained and you understand.
3rd image / attachment show where i added extra lines
IF this do not fix your problem - you could remove the following line:
\XF::logError('XenForo upgrade check failed: ' . $errorMessage);
(where do I find this? in xenforo folder: src > XF > Service > Upgrade > Checker.php
save and test again