Using PTPA Version 2019. I have a type 1 midi file I've been editing. I have loaded and saved it several times. Suddenly the last time I tried to save it the dialogue box defaulted to Seq. I changed it to.mid type 1. It saved as a .seq even though I selected .mid. I tried over and over but it will not save as a .mid. Running out of ideas I reinstalled my old PTPA V.11 and loaded in the type 1 midi file and did a simple little edit. When in tried to save the same thing happen. I selected .mid type 1 and pressed save. It had been saved as .seq just like it did in PTPA 2019. What can I do?

Check for a checkbox in Options to Save as SEQ file format.
I think it's in the file tab.
Maybe this is causing it?

I tried that but it didn't seem to work. I don't have any problem with other files. Just this particular one. It has no audio tracks. I've analyzed all the tracks using the Event Editor but haven't detected anything that looked suspicious. Saving all the other files gives no problem but this 0ne defaults to .seq and even after I manually select .mid type 1 or 0 it saves as .seq.

Maybe email it to support. See if they see anything.
Or post it somewhere for others to try.