Unable to log in to Apple Business Manager

Short version: My former boss passed away suddenly. Since his passing I have been promoted to his position. Unfortunately when he passed he took the access to ABM with him. Work has granted me access tonhis old work phone and work email but neither of these are used for the ABM login. Is there any method to discovery what login email used his email as the recovery email?

Sorry but I'm sure I may have left out some details but I'm not sure what those details may be so feel free to ask for any information I may have forgotten to include.

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u/Ambitious_Hand_2861 — 1 month ago