You had DEMi and DEM below, as written it would always just use the first dem, your next dem is not used..
So your second viewshed may not have a point1 in it.
If your running this from the IDLE or pythonwin, I’d use print commands to see what your variables are, so if it errors off you have a better clue.
I wrote what I’d use in blue below. I also shortened your output string.
One big potential problem is if your typing in the workspace path, it’s so easy to confuse the forward and back slash.
Are the points and dems in the same projection?
Since I had some time, I rewrote the code, see below in green. It works, my e-mail is William.Chappell@its.ny.gov<mailto:William.Chappell@its.ny.gov> if you want the script I used, in case copy/paste messes with the indent formats.
Good Luck, Bill