after upgrade to 4.4.1 got this error on backend, then it is unable to load latest versions info
any ajax request in system settings → installation of plugins, themes, updates, all down due this error
This is a Guzzle package that’s out of sync in your vendor/ folder — Utils::asciiToUpper() was added in guzzlehttp/psr7 2.8.0, but your install still has an older copy of that class, so the code calls a method that isn’t there. Every backend update/marketplace request goes through Guzzle, which is why they all fail.
Can you post the output of:
composer show guzzlehttp/psr7 guzzlehttp/guzzle
and let me know how you upgraded to 4.4.1 (composer update, backend updater, or manual file copy)?
The fix is almost certainly:
composer update guzzlehttp/psr7 -W
and if that doesn’t sort it, a clean rebuild:
rm -rf vendor composer.lock && composer install
Then restart PHP-FPM / your web server to clear opcache.