I didn't log into my second steam account for about a year, and today I discovered that I can only trade limited use items, like keys, duels, paints and tags. All other items are marked as non-tradeable, and steam says that I don't have the premium DLC for TF2, though I gifted it to my second account two years ago.
Also, TF2 backpack viewers say the inventory is 300 slots in size, and that those items are not marked non-tradable.
Has anybody else encountered this problem?