As a followup, I received the new "long range" temp and voltage dongle. I installed it in the battery box and tested with connecting it with the other Victron dongle under the wardrobe. It did not have enough power to reach
The dongle that is under the wardrobe (hooked to the Blue solar controller) has a cord about 4 feet long. I routed it up into the wardrobe and mounted it on the right side of the wardrobe as high as I could get it. I also brought the temp dongle out of the battery box and mounted it on the side of the box. It is epoxy watertight. The temp dongle can now see it.
Part of the problem is the temp dongle is in the battery case and shielded. The entire trailer skin is a big shield also. Having the solar controller dongle below the wardrobe with interference with all the other electronics also may play a part in it not connecting.
At least it works now.