Solution 1:

Solved. The mistake I was making was that I was exporting the "private key" part of the certificate in Keychain Access instead of the "certificate" part. As soon as I re exported the .p12 using the correct row in the list - it worked.

Images to illustrate below credit iOS

Don't select & create private key for Production certificate

Correct method:

Directly select certificate & create production certificate

Solution 2:

try this

make .csr file and download cert from developer.apple.com

while exporting select private key and certificate both at a same time and export to .p12 with any passphase.

upload tht .p12 file on firebase console.

Thanks