Tuning into frequencies

So I’m currently flying from London to Buenos Aires, and part of my route takes me over Madrid airspace, which is currently being controlled. However even after crossing into Center airspace (777 at FL340, should be okay right?) I found that the sim wouldn’t let me tune in, just kept coming up with “NO FREQUENCY”
Can’t tune into Porto, or Madrid, or anywhere else, so does anyone happen to have a fix that does not involve restarting the whole flight?

You would only be able to tune into the center frequency if within 405NM range of the emmiter, i.e., from the airport through which the controller is staffing the airspace. Was this condition satisfied by any chance?

No that’s what I eventually found. The guy was open at Valencia and I was over Portugal so understandable why that didn’t work. Thanks for the advice though

OP flagged for closure