It depends on the name of the mod file - if you want you can just rename the file to just GEL.mod.gml (or GEL.mod if you have file extensions disabled) and rename the startup.txt commands to work with that.
(tl;dr is that you can't /allowmod a mod on the frame you load it)
the fix is that you need to make a second text file (say startup2.txt), have the /allowmod command in there, and in the first text file do /loadtext startup2.txt
