Fritzbox 6690 frequently disconnects

Hello,

I have the FritzBox 6690. I am experiencing loss of connection on a weekly basis. The Power/Cable light flashes despite restarting or rebooting, and it usually takes over 2 hours for the WiFi connection to be restored. I have used the MyFritz interface to see what the issue may be. It almost always says the following: 

- IPv6 internet connection was cleared’ prefix no longer valid

- Internet connection cleared

- Cable internet not responding (no synchronisation)

 At almost 60EUR a month for the package we have, this is really not acceptable. I need a stable WiFi connection as I work remotely and handle client calls.

Any help would be appreciated - this is very frustrating!

Many thanks. 
Audrey