Devidas,
For the first error, one reason would be that you have logged onto ECC system, you opened the planned order using MD12. You must not be editing the order when you are attempting conversion.
Once you are out of the order in ECC, you should be able to activate the queue and process it.
For the second error, it could be anything. You have evidently somehow lost connectivity. Could be a network issue; talk to your basis and/or network people.
Best Regards,
DB49