"My name was found on the school admission list but Jamb CAPS portal says have not been admitted yet."

Many candidates are currently having this issue at the moment. They have been offered admission by their schools of choices but yet their admission status on JAMB CAPS still shows “NOT ADMITTED”. If you have been offered admission on a school’s website or portal but you are yet to be admitted on JAMB CAPS portal, the information here is for you.
The major reason for this is the fact that such candidates are yet to upload their O’level results on JAMB CAPS. Until your O’level results is uploaded on JAMB CAPS Portal, JAMB will not offer you any admission on their portal because you are simply not qualified for admission until you are able to provide your O’level result.
So we advise all candidates who are yet to to be admitted on JAMB CAPS Portal even after their school of choice has offered them admission to immediately proceed to any accredited JAMB CBT centre or JAMB Office to upload their O’level results on JAMB Portal.

Even if you submitted your O’level results during JAMB Registration, you are advised to re-upload the results. Remember without JAMB giving you an admission, you cant print your JAMB Admission Letter and until you have a JAMB Admission Letter, you admission is not valid. All affected candidates are therefore advised to take this serious or risk losing their admission.
After re-uploading your results, you are advised to check JAMB CAPS again after 3 days or 1 week to see if your admission status has changed to “ADMITTED”.

Source :: https://www.edutips.com.ng/reasons-why-you-may-be-admitted-on-school-admission-list-but-not-admitted-on-jamb-caps/