Last weekend, the DEX (TM) Diagnostics Exchange was down for transition to Palmetto GBA LLC management (the contractor that manages MolDx).
MolDx is posting that DEX (TM) will be down again this weekend (September 25-28) for further transition to Palmetto GBA LLC. See DEX (TM) here.
In August 2020, MolDx updated rules for using DEX (TM). It's M00148, V14 here, here.