Seriously is this the best you’ve got??!
This is the first thing you have to test. Typically, when similar issues arise, deactivating third-party plugins has been a helpful step in identifying the cause of the problem. By doing so, we can isolate the issue and investigate further.
You think both me and my web dev haven’t tried both these already??
Yes, I think, because you didn’t provide anything in your message. What you have tested? Which type of configuration do you use? Which plugins and theme installed? Have you tried to play with the htaccess file? Nothing. So, yes, I think you should test from scratch.
Disabling the 3rd party plugin is why we know it’s your plugin that’s the issue!
Our plugin? Or the conflict between our plugin and the 3rd-party plugin? Or conflict with your installed theme? Or conflict with your custom code? What exactly do we know? Nothing.
Please take the trouble to do minimal checks and provide as much information as possible so that we can reproduce the issue locally.
Regards, nK.