OP,
It looks like the sheet vinyl was perhaps stored incorrectly: full rolls, or off-cuts from rolls, should be stored vertically never laid flat. Maybe yours was stored flat?
The best you can do is to wait and hope, esp with the warm weather, that the sheet will relax ,and settle down more or less flat?
Dont do anything to it - no more cutting it in - or setting heavy objects or appliances on top of it - just wait.
If its eventually glued down then you will need to hire a heavy roller, and understand how to glue and roll.