How to get it to shut off when tank is filled

We encountered the same problem. Flushing the fill valve worked for us. https://youtu.be/Ul0V2LWSDj4 https://www.youtube.com/watch?v=AabLItDN-qk

Before installation the fill valve has to be adjusted to the proper height so that it's able to fill the tank with the proper water level. The valve is not preset as it is a universal product and it can be used with various styles and design of toilets. Not having it properly adjusted can lead to not enough water in the tank or too much to where it can overflow. If the valve is properly adjusted and the water just doesn't shut off at all then there may be debris in the fill valve that may have run through when the water was turned back on. This can sometimes cause the pipes in your home to shake and rock knocking debris loose and running into the fill valve. This can obstruct the rubber seal and prevent it from closing properly. Flushing the fill valve as shown in the troubleshoot section of our installation guide shows how to perform this purging of the fill valve. For additional information or help with your product contact Fluidmaster’s Technical Service Department as we are available Monday through Friday from 5:30 AM through 5:00 PM Pacific Standard Time. Contact options include: Chat www.fluidmaster.com/support E-Mail techsupport@fluidmaster.com and Toll Free 800-631-2011.