Zoom Not Screen Sharing For Host-(Uninstalled App Still Not Working)

I hope someone out there can offer a solution as I'm starting to get worried about this. I couldn't share my screen last week which has never been an issue before but then a good friend suggested installing zoom over the current one so I did and then it was fine. Fast forward a week and then the same issue reappeared and now installing it over the old download hasn't worked and so I tried deleting it but that didn't work either. I have a mac which is about 4 months old, not sure if that would make a difference. Any ideas or help would be much appreciated.