Hello,
I am upgrading com_jaextmanager through the JA Extension manager. Everything goes fine up to the ver. 2.7.5. However, upgrading from 2.7.5 to 2.7.6 yields the error "0 Class 'Joomla\CMS\Adapter\Adapter' not found " and the Extension manager is not accessible anymore.
If I upgrade Joomla 3 to Joomla 4 with the extension manager ver 2.7.5 then in Joomla 4 the Extension manager is also not available leading to errors.
I would appreciate any advice on this matter.
Kind regards,
Zoran
Just to let you know that I resolved this issue by installing many extensions and then installing some of them again.
I cannot figure out what was the problem, but, thank you.
Zoran
Thank you Dominic!
yes, I have another issue in another installation and upgrade of J3 to J4.
The Joomla update system keeps warning me about the "JA Tabs Plugin for Joomla 3 & Joomla 4" as a plugin that might cause problems during the upgrade. After updating the System JA Tabs through the JA Extension Manager to the newest version, 2.7.0, nothing happens. The Joomla updating system message persists.
I am not sure whether I should proceed with the upgrade or uninstall the plugin. I forgot whether I used this plugin somewhere on the website.
Kind regards,
Zoran
JA Tabs version 2.7.0 should be compatible with J!4 already, if you're using this version, you can ignore that message 
In case that you're updating to J5, try this latest package (which includes the updates for J5)
