How did this get resolved for you?
Did this resolve for you? If so, how?
Not sure if you have resolved it or not but am still posting as it might help lots of others who are encountering the same error/issue.
For the OCI passport number, enter the number that is on the top right of the photo page of your OCI booklet and should say No. followed by the number. Enter the full number including any alphabets. Example: I entered A1571548
For the British passport number,
Currently my son has 3 British passports,
1st was the oldest
2nd was the older
3rd is the latest one
Even now, my son's OCI booklet has the 1st British passport number (oldest) printed on it. However, as I used the OCI service to update his British passport details when he got his 2nd British passport, the OCI database holds the 2nd British passport number (and not the 1st, even though the OCI booklet shows the 1st British passport number).
I too faced the same issue just a few days back when trying to update my son's OCI details after getting his 3rd British passport. It didn't work when I entered the British passport number that is printed on the OCI booklet but worked when I entered the 2nd British passport number as it matched the British passport number that is currently held on their database.
If you have multiple British passports, keep entering the British passport numbers one at a time and one of those will work.
Hope this helps others.