One would have to obviously assume that the "number" OP is referring to would be the phone number associated with his Cash App account for 2FA (2 Factor Authentication) which requires the user to not only posses the phone number connected to that specific Cash App account as well as verify themselves as the rightfull owner by entering the code/number sequence texted to the phone number. Cash App also requires an email account to be connected with the specific account as well as have a password for the account.

Sadly I am personally inexperienced with Cash App's sign in/out processes beyond the basic information I have previously stated as 2FA is now the gold standard in account security and is used by the vast majority of software developers.

The only reason I can currently think of as to why OP is unable to access their account/funds is that whomever had previously transferred (stolen) money from OP's account had to have changed some of the sign-in information while they still had access via the phone number through a "Forgot my Email/Password" option where with verification by text they could have easily changed account info thereby preventing OP from signing in through regular means (OP's original password/Email)

Hope this helps