Electric Tongue Jack Issue

Glad you (hopefully) have the problem resolved. But for others reading this thread it's not the best troubleshooting process to remove your safety systems temporarily. While troubleshooting is generally when you need them the most, too easy to short something while testing and trying to fix it. Most blown fuses I've experienced occurred during troubleshooting.

A better approach would be to use your multimeter to determine that you have continuity and low resistance across the fuse and holder and then move on to the motor while leaving the fuse in place to do it's work in case you have an oopsies poking around downstream.

More than likely you jiggled something which cleared some corrosion that was adding resistance and keeping the motor from producing full torque, so it could move the screw jack once you started it by hand but couldn't start by itself. If you can get the tip of a wd40 can in there to inject that it might displace enough water to keep the corrosion from reforming for a long time. Working the screw all the way back and forth a few times and lubricating that will help as well.

I agree, I hate it when I don't nail the root cause.  If/when it fails again I just go the same route as marwayne and convert it to manual - that conversion is awesome BTW.  My last two TT's had manual cranks which never gave me one bit of trouble.  The more parts, the more opportunities for failure.  It's always good to keep things as simple as possible. 

@OG - Manual tongue jacks are usually okay until you need to crank up the trailer and the rear of the TV to hitch your WDH spring bars (especially on uneven ground). I know, I know. All you have to do is pull the trailer to level ground and then hook up the spring bars and sometimes that is not an easy option. An electric jack makes it much easier plus it is a must for folks with shoulder and back issues. 

The jack we purchased from etrailer has a manual crank for when there is a lack of power. We use a drill driver for the stabilizer jacks already so we have the socket needed to use the drill driver on the tongue jack should we have to.