PO Account Generate & Approval

Hello

We have a few POs can't be submitted for approval with Error "No Approval Found".

after investigation, we observed that the reason is a problem in charge account. The problem

is this, the charge account segment something like this 50-111112-2121-212. The new change

cause the problem is this 50-1111112-2121-M12, the fourth segment has alphanumeric M12.

if we change the segment to numeric value only all will be ok, but in case if we use

alphanumeric value we will have a problem.

Is there any restriction on account generate workflow so that account segments must be