Sorry to hear that you have problems, but can you please review the information you provided underneath, “Information on your n8n setup”? Half of it is missing, and the other half honestly does not make much sense (you use n8n cloud with Postgres?). We will then do our best to help you. Thanks!
Honestly do not have much experience with Heroku, but think it does some “interesting” stuff with turning the machines off if they are not used. Can imagine that this could cause some strange issues like potentially the one you described, triggers not firing, … . Generally probably not the best way to host an application like n8n. I would strongly recommend a proper virtual server which runs constantly.