Error Unexpected token '<', "
"... is not valid JSON
Your server is outputting HTML error messages. Go to Global Configuration, Server tab, set Error Reporting to None.
If this didn't help, there's a PHP error on your site.
Install path does not exist
Joomla! requires the PHP Gzip and ZIP extensions to be installed. If either is not installed or if it's blocked then Joomla! will be unable to install extensions. Unfortunately, a cascade of unhandled errors inside Joomla! itself will cause it to come up with the unhelpful and disorienting "Install path does not exist" error message.
Solution: ask your host to enabled the GZip and ZIP extensions in PHP. Furthermore, ask them to make sure that they are not blocking the functionality of these extensions e.g. by using disable_functions or disable_classes in their php.ini file.
Please note that we routinely see hosts disabling functions zip_open, gzuncompress, gzdeflate and gzdecode for ostensible "security reasons". First of all Joomla! WILL NOT work properly when any of these functions is unavailable. Moreover and despite what your host tells you, disabling this functions does not increase your site's security in any conceivable way. If your host denies to unblock these functions please take your site to a different host that understands how server security really works.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!