I’m just posting in case this helps others.
I was finding that ImportWP failed after an update to WordPress Core 6.7, I would get a blank screen and no errors.
After some testing, I was able to determine that the issue was actually due to the Microsoft Edge browser. After the Core updated, ImportWP launched a one-time dialogue box that I needed to accept before loading the tool. Edge never loaded that dialogue box. I am using Edge within my workplace, so I’m not sure if it is an Edge issue, or a security setting applied by my organization.
When I switched to Chrome, I was able to see the dialogue, accept it, and didn’t have issues after that.