TIP 1
The first suggestion is to ensure that you send your NIN to 55019, and not your name.
Until this year, candidates used to send their Names to 55019. However, this has changed this year has JAMB has made NIN use compulsory.

TIP 2
Ensure that the NIN is correct and that you are not sending your tracking ID number instead of NIN.

TIP 3
Ensure you have sufficient airtime on your line. To get your JAMB profile, you need to have at least One Hundred and Fifty Naira (N150) on your SIM card. Receiving JAMB profile code is not free.
So, if you don’t have airtime, make sure you recharge your line and try again.

TIP 4
Ensure your SIM card can send an SMS. The issue with some SIM cards is that they cannot even send SMS (not no 55019 only but a general issue).

Another tip is to try to send an SMS to a known line and see if they received the message. If they did not, then the problem is with your line.
However, if they did, consider the last suggestion below and others I mentioned earlier

source: https://myscholarshipbaze.com/how-to-solve-issue-of-jamb-profile-code-2021-not-received/