mac pro 4,1 stuck in broken windows starup disk: keyboard not working

Hi. I have a mac pro and after having trouble making a windows partition I decided to use an old partition i made on my imac 2013. holding alt at start up on the pro would not bring te to a boot selection screen so instead I held command and r and selected the windows partition (external hard drive) as the start up. The disk has failed and now I’m stuck with a flashing under score after the chime. I tried so many things. The keyboard simply does not work at all. Wired, not wired, windows apple. nothing. I took out the bios/rts battery. Idk what to do. I just bought this things and it was working great and now I’m just sinking in sadness