Trying to install the 'EU Cookie Compliance' Extension via the component manager...
however magento seems to want to sync forever?
i understand ! the problem you are facing !
so exactly what error its showing when you are installing extension ?
also have you tried installing by uploading all files of that extensions in app/code directory under the namespace of that extension ?
put all the extensions files in app/code/ directory under the namespace of vendor and module name and then run below commands for the same :
php bin/magento setup:upgrade php bin/magento setup:di:compile php bin/magento cache:clean php bin/magento cache:flush
Then check your extensions is installed successfully !
Hope it helps !
Which exact version of Magento are you using?
There are several threads about this kind of issues on previous versions of Magento.
Maybe one of those links can give you a clue? (there are several references)