If the Recover option described above still doesn't fix the issue, try looking at the log file that the Converter generates.
The log file will be located in C: > Users > user_name > AppData > Local > Temp
If you sort the folder contents by Date Modified the log file should be near the top - it begins with pse-conversion-log_ then the name of the Catalog you're trying to convert and will have a .txt file extension.
Open the log file in Notepad and scroll down to the end of the file. The last line will contain the name of the image that is causing the conversion to fail.
The line will start something like created media a:772 for file "image_location_and_name".
Make a note of the image location and name.
Open up Photoshop Album and delete that image from the catalog (you've kept a note of the image location so you can add it back to the catalog once you're up-and-running in Elements 2020).
Quit Photoshop Album and try the Converter once more. If it fails again, which is possible as you appear to have a very large catalog of images, then just go through the new log file and remove the image from the catalog that is causing the problem. Keep repeating this process until the conversion is successful.