If it's in different format, the "next" button won't be clickable (grayed-out);
If it's the wrong seed, it will be invalid because there's a checksum with both BIP39 seed and Electrum's native seed,
unless, he click BIP39 in the option (somehow discussed above).

And there's no point in replying to a topic which was abandoned by the OP.
Let's just wait for his reply.