Horseman is correct - it's only one Imperial Palace on the Itallian Peninsular (Scilly and the Northern Itallian Gallic provinces included) that is not in Rome. This Palace can belong to any Roman faction. Research into the subject also shows no limit into the number of turns the player has to wait for them to be triggered in 1.5 - anytime will do, although in earlier patches some did think that a date restriction did exist.
I do recall a problem like this occuring before, although my searches aren't yeilding anything useful. I think the only solution was to try and find an old save game before an Imperial Palace was built in the triggering regions. Hopefully the reforms would be triggered second time round.
Good luck![]()
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