Someone made a transfer to my First bank account using ATM transer on Friday by 10.45 PM , it showed successful and the name corresponds, up till now(Sunday morning) there is no money in my account and no reversal yet according to him, what could be the problem?

It's possible your account has been credited without you receiving the alert due to network hence use your ATM card to check your balance in the next available terminal or use the mobile app. Transfer via the ATM is facilitated by Interswitch, there is always delay in applying the fund to the beneficiary unlike the NIP.

amedualiyu:
It's possible your account has been credited without you receiving the alert due to network hence use your ATM card to check your balance in the next available terminal or use the mobile app. Transfer via the ATM is facilitated by Interswitch, there is always delay in applying the fund to the beneficiary unlike the NIP.

I do check my account balance every hour using the USSD code