Frankly, I believe this is strange unless there exists any rule in your government that does not allow documents over six months old to be accepted. Once a certificate gets issued by any authority, it stays as it is throughout one's life. I doubt you will be able to get hold of another certified copy from the Qatari government. Try explaining things to some senior officer at your embassy and hopefully he may understand. Usually, people at embassies are cooperative and helpful especially to their own nationals.