Firstly, you have to have activated the script every time you start the game. Assuming you did this there are several things that might be happening.

In terms of settlements without the Camillan Era icon, during that era you CANNOT build factional MICs there. You can build the regional MICs and this is where you will get most of your decent ranged units and cavalry from the Greeks and Celts. After Polybian reforms occur, you can build factional MICS in Rhegion, Taras, Bononia, Mediolanum, and Venetia. Thats all. All other settlements will have to wait for the Marian Reforms which are a long ways off.

In terms of Polybian reforms, there is a year that the Polybians must occur at. Check the FAQ for the year, I cant remember off the top of my head. Secondly you must have conquered Segesta and Bononia, along with Syracuse and Lilybaneum if I'm not mistaken. Then, the Polybians don't necessarily happen immediately, I believe like the Celtic reforms you will have to wait several seasons for them to occur. Then, after you get the Polybian reform marker, you have to upgrade you Factional MIC's to gain access to Polybian units.

Also, Eqvites Extraordinarii and Pedites Extraordinarii are available during both Camillan and Polyibian periods which explains why they are available.

Lastly, read the FAQ. It will answer all your questions much better than me.