A dead spin is a spin that returns nothing: no line win, no feature, no prize. On most slots, dead spins are the most common result.
How many you see depends on the game's hit frequency and volatility. High-volatility games, which save much of their return for rare features, can produce long runs of dead spins in the base game. That is how they are designed, not a sign that a game is broken or about to pay.
A run of dead spins also does not make a win more likely. Each spin is decided independently by the RNG, so the chance of a win is the same on the next spin as on the first.
Some studios add small consolation mechanics, such as random respins or mystery symbols, partly to break up dead spins. These are part of the maths model and are already counted in the published RTP.