Eagle stores temporary files in a cache, which can sometimes become corrupted. You can clean the cache to solve this issue. If you are working with custom libraries or packages, make sure there are no corrupted or conflicting files. Try to generate a package using a default library to see if the issue persists. If the issue persists, consider reinstalling Eagle. Uninstall the software, delete any remaining configuration files, and then perform a fresh installation. If the issue is specific to Eagle 9.6.2, you can try another version. Someone faced this error with an old version and corrected it. https://forums.autodesk.com/t5/eagle-forum/package-generator-could-not-be-generated/td-p/11566872
Since you are using Eagle, you will definitely design and PCBs. If you want to have an idea about the cost of different PCBs, you can see here:
https://www.allpcb.com/blog/pcb-ordering/pcb-cost-per-unit.html
