hi james, please start a new thread for this issue. so that we don't fill this one with troubleshooting for issues that aren't related.
in this case i created a brand new study with the basic setup and it worked. meaning that it is a setting that you have or boundary condition.
i suppressed everything you had in the tree. same problem.
switched your selections for fluid and solid. same problem.
when i dug into your initial conditions it looks like you set turbulence length to 0m. i entered a value and it worked. generally it isn't recommended to change that value unless you have data for it.