To the OP: Are you sure you are working with VHS-C tapes? If you are confusing VHS-C with 8mm or some other size/format, that could explain the “no signal” message, no matter what the tape condition is.
Discussions like this often make the claim that all tapes over X years are no good. While I don’t have any video tapes over 40 years old, I do have many audio tapes with varying ages, up to 65 years old, all of which have been stored in the same environment for their lifetime.
I have some audio tapes from the 1950’s that are perfectly playable and show very little signs of age (slight cupping which flattens when passed by playback heads). And I have tapes from the 1970’s that are too gummed up to play at all. Some of these are stored next to other tapes of the same age, same brand, same formula, that are perfectly playable.
So I can conclude that while age may be a big factor, it is not the only one.
Let me provide an anecdote. Around 1975, I was using so much audio tape that I was buying it in bulk – a case of 10" “pancake” spools that were rolled off into smaller hubs. Opening a new box direct from the distributor one day, I found that the tape was shedding badly when passing the heads of a professional recorder. After only a minute or two, I had to clean the heads again.
Maybe a bad reel? But the same thing happened with other reels in this box. Since this was professional Ampex 206, I called the manufacturer’s rep who came by and saw what I was doing. I gave him the entire box and he exchanged it with a new one. The rep said, “It must have been a bad batch.” I wonder how many boxes of this batch are still in someone’s library, but were bad from the start?
I have a collection of cassette tapes from the same era. Most are entirely playable; a few are not. I once had a custom house wind up a batch of cassette blanks in odd lengths since I found the commercial lengths a waste. I don’t know what kind of tape they used, but I always thought it was generic. Nevertheless, none of these have ever become unplayable.
So brand or formula is no guarantee of longevity; even high-quality tapes can become defective, and low quality tapes aren’t necessarily junk over time.