We’re regular users … just like you … w/o access to any of your account info.
So “No” … nobody here can tell you why.
That said, recent or unusual address moves, mis-matched account addresses, name changes, using different versions of the “same” name (e.g. using “Betty” vice “Elizabeth”) — or outright theft of your identity — are examples of items which can complicate the verification processes.
A detailed review of your 3x free annual credit reports from the “Big Three” CRAs might be a good place to start and might possibly yield some clues.