You are using osTicket-Awesome-1.10.1-v1.3.
I haven’t received any complaints from anyone regarding page load times using that version, and it has been out since the end of April. Hmmm.
Please try loading pages from the Demos on the same devices and let me know if you’re experiencing the same slowness.
https://osticketawesome.com/1.10.1/
https://osticketawesome.com/1.10.1/scp
Do you have APCu installed on your IIS server? I do find that it makes a difference in osTicket page load times on a Linux server.
It might help for me to have a look at your setup. Please create an Agent account for me (Admin Panel > Agents > Add New Agent) with admin privileges using info@osticketawesome.com.