http Errors since trying plug in

Hi, I installed your plug in recently, it had worked fine in other sites for me, but this time it didn’t work AND it seems to have caused an issue in the media library.
We now get http error message when trying to upload PDFs, and now jpgs, word files we uploading ok and I am trying get this fixed. I had already deactivated the plugin (assumed they didn’t have imagemagick or whatever is needed on server (I generally haven’t dealt with their hosting account just WP dashboard). As I hunted for solutions got the idea this might be related, so deleted the plugin but still getting errors. Now it won’t always show the image in the editor view in one case.

Any help in debugging this for my client would be MUCH appreciated…as well as understanding what might be things to check before using since it seem to be sensitive to something on the server end beyond WP…
thanks!

https://wordpress.org/plugins/pdf-image-generator/