This might sound silly, even stupid! But have you tried a different computer? Do you have any other computer - Mac, Windows, Linux - that you can use to try?
A fresh installation of OpenLP onto a different computer would tell you different things.
You could also back up your data on your current computer and do a fresh installation on it. See what happens. But don't do anything like that without having backed up your data!
These things aren't clutching at straws. They're all part of problem-solving as I've been taught. But it's always easier to follow proper problem-solving procedures when you don't have any emotional energy attached or invested in a task. I often find myself asking silly questions to which I should - and do! - know the answer. But I have so much emotional energy attached to a project, I can't ask or answer simple questions. All of that was to say there's no criticism of you for not trying different things. Some people might call them basic things.
I'll be interested to know how you get on.