Firstly make SURE you are testing with the new IDs!  The old rad rainstorm IDs no longer work as of version 1.3!  They are as follows (replace first 2 digits with your True Storms load order position):

TrueStormsRadStormRainHeavy [WTHR:04000859]
TrueStormsRadStormRainLight [WTHR:0400085A]

Secondly, True Storms v1.3 fixes two MAJOR VANILLA bugs with radiation in the Glowing Sea that would cause radiation damage to drop or stop completely.  Make sure you're running TS v1.3 or above!

That said, there are a few reasons why this could be happening:

• If you have the AQUABOY / AQUAGIRL perk, you are resistant to radiation water, which includes rain in this mod!  I may include an option to remove this restriction, but it made logical sense.
• If you have TGM (god mode) active, you will NOT receive rad rain damage, OR Glowing Sea damage, even if you disable TGM after forcing the weather.  You need to disable god mode, force weather to clear, THEN back to one of the radiation rains.
• If you loaded an old game in the glowing sea, or while you were in the middle of a rad storm (which, if you followed my update procedure should NOT be the case) you will need to completely leave the area, go inside an indoor with a loading screen, force clear weather (fw 2b52a), THEN go back to the radiation area.  The game triggers things at specific times under specific conditions, and you may be mistaking this for a bug.
• You may be experiencing one of the Bethesda bugs that I fixed.  If you're receiving less than 1 rad per second in the Glowing Sea, even if you're naked, enter and exit power armor while the storm is happening, or equip/unequip a Hazmat Suit.