Did you load the map in the same playlist as the last? If you hit "disconnect" in the singleplayer lobby to switch to a different playlist (or just switched to a different playlist), then the weapons will lock again. For example, if you have a playlist with only Jundland Waste in it, the weapons will be locked during the first round. If you let the map load again after the first round ends, then the weapons will be unlocked for subsequent rounds on the map until you hit "disconnect" in the lobby. If you were to select a different map (or even the same one) afterwards, the weapons will be locked again until the first round of that playlist is complete. For an example of a multi-map playlist, if you were to have Rhen Vhar Ice Plains and Endor Strike Team in one playlist, then the weapons will be locked during the first round on Rhen Vhar Ice Plains. Once the next round switches to Endor Strike Team, the weapons will be unlocked for that round and subsequent rounds on both maps until you hit "disconnect" in the lobby. Also, I can tell they are unlocked because their frames in the selection menu won't be greyed out and can be dragged and dropped into the weapon slot.