PHP > 7.1 compatibility issue

[Ralf Klis]

I've already done it on support forum but since PHP 7.1 is officially outdated now this is a quite high priority issue.

This plugin doesn’t work on PHP 7.2, 7.3 and 7.4 due to outdated MPDF version (you’re about 2 major releases behind).

https://wordpress.org/support/topic/plugin-not-compatible-with-php-7-1-2/