Hi @Margie !
If you have already performed the basic troubleshooting such as: checking filters in Inbox; checking if this user actually received envelopes after Jan/24; if this user is accessing the correct account; if this user accidentally deleted the envelopes, and other simple things, so I believe that this specific user may have two or more accounts linked to the exact same email address and the envelopes after Jan/24 are going to this new account.
Users can create more than one account linked to the same email address, including trial and corporate accounts. To check this situation, the best way is to ask this user to open a ticket with the Technical Support team, where they can investigate and check how many accounts are linked to this user. If possible, ask to open a ticket by sharing the ID of an envelope that was sent after Jan/24 and is not showing in their inbox.
I hope this can help you!
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