The default upload limit (importing SQL files, etc.) in phpMyAdmin is 2MB.

It’s quite easy to increase it. In this case, Plesk is running on a server Linux CentOS 7 server.

• Navigate to /usr/local/psa/admin/conf
• Edit file php.ini and set the following two lines to whatever you want to limit to be in MB (in this example 64MB).
  • post_max_size = 64M
  • upload_max_filesize = 64M

• Restart the server.
  It normally would be sufficient to restart the Apache web service, but this didn’t work for me. I assume because phpMyAdmin in Plesk is running on its own web service. I found it easier and quicker just to restart the whole server.