The messages in your browser console are just notices that don't affect the functionality of anything on the page.
If you get a white screen when trying to edit a template it means you almost certainly have PHP errors on the server, and you need to check you debug.log to find what they are.
If you haven't already, turn on the debug log by editing your wp-config.php file and change the line with WP_DEBUG like so:
That will create a debug.log file in your /wp-content/ directory which you can examine in any text editor. Try editing the template again and then inspect the log.
I also suggest you try disabling all plugins except for Types and Blocks.
Can you edit the template then?
If so it seems a conflict with another plugin is causing the problem, and you should be able to determine which one by a process of elimination.
The debug logger for wordpress won't generate any information in the console because the blank screen is an indication of a PHP error.
The debug functions that Nigel has provided should generate a debug.log file in your /wp-content/ folder.
If you're able to find this file can you open it and send me the contents of the file ? If there isn't anything generate then there should be a log on your server itself that keeps a list of all the php errors on the server.
What you can do is to contact your hosting company to see if they can point you to where the server logs are.
Unfortunately we are not able to debug issues on localhost, is there any way for you to place this on a live server instance and check if the issue still remains?
This way we can have access here to check the issues to see what we can find.
Thank you I was able to log in and verify that I can in fact see the issue. Would it be ok if I took a copy of this site so that I can run it here locally?
I would like to see what errors would appear on my end. Right now when its on your servers all i'm seeing is [12-Nov-2020 15:44:16 UTC] PHP Fatal error: Maximum execution time of 120 seconds exceeded in C:\xampp\apps\wordpress\htdocs\wp-content\plugins\types-access\legacy\types-access.php on line 5
Which doesn't give a lot of information as to what is happening.
Based on my testing, when i disabled the WP REST API Controller plugin the content templates load fine.
It loads with every other plugin enabled except WP REST API Controller. So I would recommend getting in touch with the support team for this plugin for them to have a look at it because no error is being generated in PHP or on the site.