How do you start Houdini? Don't double click a hip file. Start Houdini from the Houdini Command Line Tools.
Does anything about Arnold show up anywhere? Did you see anything logged in the Houdini Console at startup?
Are you sure you are using the right version?
htoa-5.3.0_r233605f_houdini-18.0.499
htoa-5.5.0.1_r45f2926_houdini-18.5.408
Your env is a mix of the 2
“htoa-5.5.0.1_r45f2926_houdini-18.0.499”
If you are using Windows 10 Pro Verision 20H2
You have to move you env.file from
C:\Users\YOUR_NAME\Documents\houdini18.5
to
C:\Users\YOUR_NAME\OneDrive\Documents\houdini18.5
Can you post the details from Help > About Houdini > Show Details?
I don't see anything obviously wrong. But there should be more messages logged by HtoA at startup.
Can you get a Process Monitor log? That will show what's happening at startup.