No option to rejoin

Disconnected from a comp game “lost connection”, signed back into the game and no option to rejoin. just a 15 min suspension.

Sometimes the match will either cancel if you disconnected very early. It cancels as a benefit to all remaining players since it is not confirmed that you can reliably play in the game at the time with a bad connection. Penalties are automatically enforced in this case which you can learn about here: