Happened with me too, got thrown out in the middle of a game and my internet was fine
Lost due to chess.com server issue?

During the last rapid game I played, I lost connection to the website, so I checked the connection, which was completely fine, and tried to reload the site. The site loaded, but a message "There is some problem in connecting. Please wait" in a blue box kept showing up and couldn't connect to the game, so this was not an issue on my end. I finally was able to connect 10-15 minutes later but my time was completed by then and I lost, and my last move hadn't been recorded.
Also it looks like it was not only me having the issue: https://www.chess.com/forum/view/general/rapid-stuck-at-starting-soon
There was a server restart and an issue around an hour later that was quickly fixed

Yeah this is ridiculous I "lost on time" even though the screen showed my move was made and opponent's turn

Here's a weird glitch. I was waiting on my opponent to move. Then, all of a sudden, Chess.com says it's MY turn to move and my clock was considerably, but it wouldn't let me move! Then I lost because I "abandoned" the game. But I was waiting on my opponent!
There was a server issue around the time you posted.
During the last rapid game I played, I lost connection to the website, so I checked the connection, which was completely fine, and tried to reload the site. The site loaded, but a message "There is some problem in connecting. Please wait" in a blue box kept showing up and couldn't connect to the game, so this was not an issue on my end. I finally was able to connect 10-15 minutes later but my time was completed by then and I lost, and my last move hadn't been recorded.
Also it looks like it was not only me having the issue: https://www.chess.com/forum/view/general/rapid-stuck-at-starting-soon