I'm having a bug taking the Rift in the Imperial Civil War questline; after raiding the caravan, Rikke won't have the dialogue option to let me go and assault Fort Greenwall.

I have already tried examining the map, moving Rikke to a different camp and asking her there, talking to the quartermaster/using the cooking pot then talking to Rikke, talking to Tullius about war progress, and even spawned separate Rikkes to see if it'd work. So, may I ask for any suggestion to try and solve this?

Thanks.

Try sneak attacking Rikke or attacking her until she falls to her knees, this sometimes allows her to give the "reporting in" dialogue option.

Note: Doing this "may" cause you to incur a bounty and/or cause her (and other soldiers) to become hostile, so you may need to yield to her and/or pay off your bounty in Riften. Also you may want to reload a save prior to spawning copies of Rikke and/or using console commands to try to resolve this issue.