First, check that the 1amp inline fuse that is connected to the BIM is not tripped. You can find this under the jump seat drivers side. Usually the orange wire attached with a fuse. However, if the tank monitor display is working, the fuse is probably fine.
Second, check underneath the drivers side where the fresh water tank is located around the macerator pump area. The full sensor is the one on the top. Pretty easy to access and see. Check to make sure that nothing is stuck on the outside of the sensor or maybe something got attached to it while driving.
Third, these sensors are on the outside so there is no chance of anything getting stuck to them from the inside. However, sometimes at RV parks or other locations where you fill and if they have well water, it can be hard water and cause some build up on the inside of the tank on the opposite side of the sensors. I would do a tank cleaning with some bleach at the higher dose and leave it overnight to see if that clears it up. Totally safe to do and we do it about twice per year.
Lastly, make sure that the top full sensor didn't get cut and the wires are attached correctly.
Good luck and hope this helps.
From the manual:
Potable water systems require periodic maintenance to deliver a consistent flow of fresh water. Depending on use and the environment the system is subject to, sanitizing is recommended prior to storing and before using the water system after a period of storage. Systems with new components, or ones that have been subjected to contamination should also be disinfected as follows:
1. Use one of the following methods to determine the amount of common household bleach needed to sanitize the tank.
a. Multiply “gallons of tank capacity” by 0.13; the result is the ounces of bleach needed to sanitize the tank.
b. Multiply “Liters of tank capacity” by 1.0; the result is the milliliters of bleach needed to sanitize the tank.
2. Mix the proper amount of bleach into a container of water.
3. Pour the correct amount of solution (water/bleach) into the Fresh Water tank and fill with potable water.
4. Open all faucets (hot and cold) allowing the water to run until the distinct odor of chlorine is detected.
5. The standard solution must have 4 hours of contact time to disinfect completely. Doubling the solution concentration will allow for contact time of one (1) hour.
6. When the contact time is completed, drain the tank. Refill with potable water and flush the plumbing of all sanitizing solution.