Bounding issues can cause a great number of problems, but you weren’t able to have the water function even before runtime, so I’m thinking that’s not the case. I’m unsure why your water layer didn’t generate when you installed the water plugin, as it should for any map you place any water in, as long as edit layers is enabled when you place the water object in.
Could you try deleting the water systems (the brush, the ocean, the waterzone, and the rivers, all of em), and try reintroducing them. Does it make the water layer? I wonder if it has to be generated on launch or just have the name Water in this case. let’s test that out.
Worst comes to worst, (and if you’re comfortable with it) I’ll take your heightmap, make a project, get the rivers/ocean working, then pass it back to you. It’s not ideal but in this case, I can’t narrow down why it’s failing for you.