TB PC-valid, private gpg key.asc, fails decrypting ONLY on TB mobile yet healthy on OpenKeyChain

Hi, I have exported a from my Debian linux GnuPG private ed25519 keyring a private armor format private.asc file for upload into my mobile OpenKeyChain (showing healthy) and imported on my mobile thunderbird version 21.1 the private key from OpenKeyChain. When receiving an encrypted email, my thunderbird PC version decrypts while my Mobile thunderbird show an error in decryption operation: I can read encrypted email on my PC, not on my mobile. When I send a encrypted message From my mobile TB exact identical key to another of my email addresses, the email received into my mobile TB is automatically showing decrypted. This email is also decrypted on my PC thunderbird. The TB account on both devices are the same. The private key is the same. The email provider is the same. The email addresses are identities of the the same key. I have had this problem before. I have resolved this in the past and can no longer figure out how. Any intuition? cheers.