President of the board non board member blocked changed post office box and bank account from acting board voted manager of condo association what can we do?

That depends on who 'we' might be. From your question, it's unclear who's a non-board member, and who's the manager, and who is 'we'.

If you are other members of the board, you can enlist the support of your association's attorney to compel the (non-board member) people in possession of the association's assets -- the mail box and the bank account -- to turn them over.

If the manager is a property manager with whom the association has a contract, remind the manager that s/he is a vendor, not an owner, not a corporate officer, but a paid partner.

If you are an owner, you need to work through your board and proceed as above.

If the board is fractured and this is a rift among board members, go read your governing documents and discover your responsibilities -- all of you, to perform your duties with a legal responsibility to the association.

Invite your association attorney to your board meeting and require that all board members attend. State the facts, bring the evidence and work with the attorney to free the association from this situation so that assessments can be collected and bills paid.