Ok, wasn't sure if you had been. I presumed incorrectly.
If your going from modem to DIR and it's been working then that configuration should still work.
If anything, you might do a full factory reset on the router with out it being connected to modem, re-load a fresh same version FW file using IE11 or FF, then factory reset then set up the router from scratch with the modem connected and see now it works.