Have you tried Sony recommendation for stuck cassette inside the carriage or unresponsive cassette inside? According to the consumer Sony mini DV manuals, sometimes it’s caused by condensed moisture inside and other times electronics becomes jammed.

At any rate, if electronics becomes jammed and the carriage would not work, remove the battery and disconnect the AC power altogether and then try again see if the camcorder responds after reconnecting. And if the carriage door is already open, try to air it out with gentle air, and then try again by reconnecting.

TS