elbow pain-1 arm pushups?

Hi guys new on this forum( but not a new athlete ). Basically im following Convict Conditioning and im ont the 9th step for 1 arm pushups.

This is the step,

I basically feel elbow pain while performing. I dont want to end up with tendonitis or anything. Should i stop ? Or is it most likely a form issue?

Where is the pain in your elbow?

Pain is the middle of elbow and it took me around 6-8 months to progress.