Help! The links to my videos aren't working when I share them with students. Only works sometimes.

Can anyone help me?  I teach ballet and I'm recording my classes but lately the links aren't working. Why Not?  Can you help? I have a basic plan and only 1 MG of data. My classes are an hour long, and usually I can keep 3 or 4 classes in there. But lately I've been having trouble. Can you help?  Also, Is there a way to get just like a little more storage space and not have to advance to a huge plan?  I just teach ballet classes, that's it. Small classes. Nothing fancy. 

Thank you in advance,

Sarah