You can login through FTP then edit the wp-config.php file and find the line: define( 'WP_DEBUG', false );. Set it to true then save the file. Log back in the admin area and you should be able to see some more error information when you redo the steps you are having issues with.
If you are getting an error message that suggests: Fatal error: Allowed memory size of xxxxx bytes exhausted, it means that you need to have the PHP memory limit of your site increased.
To do this, please edit your wp-config.php file and insert these lines:
We have successfully logged in. Regretfully we cannot see the error or on which page it appears. Could you please change role of the given user credentials to at least a Super Admin so that we will have full control of the multisite and be able to check every section of your multi site setup?
When you visit the Network admin, it will result to a fatal error. Please login to your ftp and browse to the plugins section wp-content/plugins/. You will need to delete tco-email-forms folder because it is causing the issue.
This ticket is showing up in unresolved list of tickets. However, I am not able to figure out the information you have added after the response by my colleague, Thai.
Can you please let us know? If possible and to avoid any confusion, I suggest you to create a new ticket and if the query is related then you can give a reference to this ticket for fast response time.