Thanks for your reply!
I checked with the hosting company and Gzip is indeed enabled by default because they’re using LiteSpeed servers.
Regarding the Static File headers, I have not edited the .htaccess file and I’m not using Cloudflare. Could this issue also be connected to the Litespeed server?
Many thanks!
For the record, I’ve been in touch with Waseem who has resolved the issue. This is really a five-star developer who delivers top-notch quality plugins. Controlled Admin Access is indispensable for me and highly recommended. Thank you, Waseem!