yup you can still enter qatar at no worries at all,, 1st locate the validity of your previous visa written on the copy,, normally it only has a 6month validity,so if your previous visa was issued last august, it will expire at around the month of february.. if a visa was not used or process within its validity, it automatically expires. just wait it out so you can use your new entry visa. in addition,, since you don't know the date just assume the duration from time they issue the 1st visa then compute the 6 month duration.. we have the same visa btw..