I’ve read through a thread about the same problem (from Jan 2018). It was instructed to check the Aggregate inline JS on Autoptimize. On my site, it’s already checked on my Autoptimize settings. However, the menu on mobile is still not clickable. I tried unchecking it too but the issue persists.
I am seeing some errors in the console which look to be related to adverts.
Can you remove any advert scripts to see if this is interfering.
If that doesn’t work, can you disable all other plugins except GP Premium ( including Cookie Consent ) – if this fixes the problem, re-enable them one by one to see which one is causing the problem.