I put a vhs tape in an the vcr turns off by it self a green light keeps flashing by where it says cst in. I have a Hitachi DVD/VCR COMBO DV-PF2U. I also can not get the tape out

Unplug the power supply for thirty seconds and plug back in, this will reset the processor and might eject the tape. If this fails the next step is remove the top of the combo unit this will give access to the vcr tape, if the tape is spewed in the machine and wrapped around the video head and other mechanical parts use scissors to cut the tape and carefully removing the particles, press power to eject the tape for normal operation. However! if the vcr tape is okay, there may be a loading problem, broken drive belt, bad idler assembly to name a few, this is where a technician will be needed but may not justify cost.