Sorry, I'm not very familiar with the "Help Desk Audit" plugin since I dont use it. (Although I did just install it for the first time earlier today so this will be changing.)
I am not seeing any pre-requisites for the plugin other than the version of osTicket (1.14+).
I am running osTicket 1.15.2 under IIS 10 with php 7.3.19.
I am also not seeing the errors that you were getting.