Beyond what is above, take a look at: https://www.reddit.com/r/Namecoin/comments/kycern/how_to_get_nmc_out_of_coinomi/ IIRC NMC does some odd things with their keys / wallets. It's been a while but I think the above might help. If not the subreddit I posted above does seem to be somewhat active, they might be able to help.