It has happened to me in the south of France. One FIS frequency just had a recording stating that it was closed, and on another frequency I was told I was outside their service area. Given all the traffic and military zones in the area, it didn’t feel good.
When did that happen, and was it a weekday or a weekend?
Lack of ATC coverage in France would be a huge problem on many VFR flights, where the airspace is so complex that one almost cannot plan an OCAS transit. One would end up flying in the Class E airspace (base FL065 generally) as that keeps you away from nearly all stuff, and getting enroute notams would be good enough.
That was about 2 years ago on a weekend, VFR between Avignon and Aix-en-Provence (the part with no FIS; maybe even a bit further north). AFAIR flying high is not an option around there due to airspace.