Tactical Maps Reincarnated maps are too big for D&D Beyond VTT. I purchased these maps thinking they would be compatible with the company that made them. Am I doing something wrong? The map editor only supports up to 10 mb. 

Those maps were released years (literally) before Maps launched and have not been optimised for Maps. Instead they're optimised for printing, hence the high resolution

Edit: it should be noted that existing maps will be backfilled into Maps in the future

I do not have these particular maps, but there are many ways to resave image files to make them smaller at the expense of some resolution. You might want to try that.

You can buy the Tactical Maps Reincarnated through D&D Beyond.
But those are just JPG images.
You would need a VTT. https://19216811.cam/
I would suggest Fantasy Grounds or maybe Foundry VTT.
Possibly Roll20.net

Quote from tryol0 >>

You can buy the Tactical Maps Reincarnated through D&D Beyond.
But those are just JPG images.
You would need a VTT.
I would suggest Fantasy Grounds or maybe Foundry VTT.
Possibly Roll20.net

 They're referring to the newly released Maps alpha on D&D Beyond