Sounds to me like your linkage needs adjusting,try slackening the pinchbolt and pushing the linkage forward to give you more purchase forward,the gears will be there somewhere I'm sure!!!!
Also,you could prove its the linkage by manually selecting first on the box with the linkage disconnected and see if its there,do the same with third and fifth,you don't need to drive it,just let the clutch up and see if it bites. Rules the box out then.