My Network are not consistent

I installed a new router but my Network intermittent disconnect and come back on its own, router Model CISCO Meraki with cellular data back up plan; The router doesn't have access point, so I added up NETGEAR Wireless Desktop Access Point (WAC104), but my network now is not consistent keep going down and up every 2 hours, I never had any issues with the previous router Wi-Fi issues, how can I diagnose and know what is the issue is it to from the provider or access point all the new router. Any help I would appreciate it.