why is adobe not saving my signature

I make my signature and then save it  

I get an error message 

so when I go back to it's not there 

I am using windows 10 and a mobile app

it worked fine for years but I needed to add initials and I tried to add them on the app and for some reason, it took out my signature now it won't save.

also, does anyone know how to use my keyboard on the app to make a signature or initials