Also, "where" is the solenoid that you replaced? Mine ('88 Jamboree, '87 E350 chassis) has a total of 4. The actual starter solenoid is on the inside fender on the passenger side, right next to the starting battery. There are 3 additional solenoids all on the driver side under the hood as well; emergency start solenoid (high on the firewall above the brake reservoir), the charge solenoid to allow the alternator to charge the house battery (behind the headlight), and the house battery main disconnect switch (latching relay behind grille under the house battery).
I had the same issue a season or two ago; replaced the starter solenoid and the starter to no avail. Mine turned out to be the battery, but if you've already replaced that, not sure what to tell you other than cables/connections, especially if you can intermittently get it to crank/start. Cables/connections are the only logical thing left (as if logic ever has anything to do with RVing!!).