no GPS signal after installing amp and new speakers

Hello there.

I recently had a new sound system installed (amp, speakers and sub connected to the original head unit). A couple of days later I noticed that the navigation system has no signal and the clock is showing the wrong time.
Of course I have the suspicion that something went wrong during the installation, however wanted to see if other people may have had similar experience with missing GPS signal so that I can better pinpoint the issue when returning to the shop.

I know that the ANC module was disconnected as part of the audio upgrade as it was causing distortion to the new system, however I don't think this would have an impact on the GPS?
May be a loose cable? Is the GPS antenna located near the windscreen?

Thank you for your help.