I have myself in the past run into many zones that I could not enter. As of late, there seem to be a ton of new players on that are asking the same thing in game about what zones are and are not locked. I try to help with all the ones I know, but I'm sure I don't know them all. I would like to get a full list of what zones are locked here so we can use it as a reference wham asked, or if we just don't remember them all. The ones I know are as follows:
Ssra Temple
Planes of Power:
Halls of Honor ( used for custom content )
Plane of Fire ( enterable custom zone with original mobs, but zero loot )
Plane of Storms ( used for custom content )
Plane of Tactics
Plane of Justice can be entered, but PoJ Trials do not work.
Plane of Water (I have crashed everytime I have tried, so may just be me )
Plane of Time ( used for custom content )
Plane of Earth
Plane of Air ( Kingdom of Wind, not PoSky )
Gates of Discord:
All of the Ikky trials
Kod'Taz
Texvu
Tacvi ( used for custom content )
Qvic ( used for custom content )
Uqua
Inktuta (sp?)
Vxed
Tipt
Riwi & Qunimi ( I have crashed everytime I've tried, so may just be me )
Dragons of Norrath:
Stillmoon is listed on the teleporter, but you can't actually go there.
All zones marked ( used for custom content ) are usable, but you will not find any of the original mobs or loot.
Would like to add that Halls of Honor has 2 zones, hohonora and hohonorb, the first of which is used for custom content, and the second, the Temple of Marr (often referred to as hohb) being inaccessible. In HoHB, you would fight Mithaniel Marr for some crappy loot and part of the Elemental flag.
Plane of Time also has 2 zones, Plane of Time A (which is used for custom content), and Plane of Time B, which you just can't get to.
Any time I've tried to enter the Plane of Water or the Plane of Air (not to be confused with the Plane of Sky (airplane) being used for T3/4 bosses) it woudl tell me I am not yet experienced enough to enter the elemental planes (meaning I am not flagged).
The Saryrn script in Plane of Torment doesn't work, and I think a friend said the Carpin cycle in Crypt of Decay is broken.
I've been told Nektulos does not work, but haven't actually checked myself.