Hi, First you have custom coded plugins that were coded to work for the Learnpress plugin version of that time. So whenever you update the Learnpress its causing all sorts of problems and issues as the compatibility is affected between the plugins.
So we have to work for that if you need a permanent solution which can be time consuming.
I can help you solve the issues currently faced starting with and fixing certificate generation problem first and then move on with others and in the mean time discussing permanent solution to such situation. Let me know your thoughts and we will move forward on it.
I am a senior full-stack developer with 8+ years of experience with core skills in Php, WordPress websites, WordPress plugins development, APIs development, Elementor, Divi, WP LMS, WordPress responsive themes and WordPress speed/performance optimization
Let me know when you would like to start and i will be happy to discuss before starting on it.
Regards
Imran