If you missed setting up as a validator pre-genesis, this means you must set up to become one post-genesis. It is not possible to add pre-genesis validators once the chain has been launched (as by definition). Instead, any full-node can become a validator through self-bonding NAM tokens.
When facing CometBFT issues as a validator, the most common cause of the issue is that we are running the wrong version of CometBFT. Keep an eye on the testnet docs here
Note that the common debug statement
Error reconnecting to peersdoes not mean that your node is not working properly. Instead, it means there exists at least one validator on the network not working properly. To check whether this is a problem on your end, note the block height and see if it corresponds to the blockheight at https://namada.world (opens in a new tab)