Hi pcwolf,

This issue is known as an error which is caused by MySQL or jommla, so please try to set the configuration.php or grant permission.

Besides, this link provide the solution for this issue:

https://besthostingforjoomla.com/fix-joomla-error-displaying-the-error-page-application-instantiation-error/.

Note: This response contains a reference to a third party World Wide Web site. Microsoft is providing this information as a convenience to you. 

Microsoft does not control these sites and has not tested any software or information found on these sites;

Therefore, Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there.

There are inherent dangers in the use of any software found on the Internet, and Microsoft cautions you to make sure that you completely understand the risk before retrieving any software from the Internet.

Best Regards,

Yuk Ding