Calendar editing is working erratically only

Calendar editing is not working properly w my iPhone 11 nor on my new iPad Pro only erratically, with everything set the same, from one moment to the next! What is going on? The advice given is incorrect, or lacking understanding, I do NOT get the editing choice when I want to change an appointment, no matter what advice I follow w email settings etc. Sometimes it just comes up with the notice that ’ this is a repeating event’ with no choice to EDIT or delete it! It is the most irritating change for me on both new devices! I never had these problems on my old devices. HELP PLEASE.