Main Flow Path errors

[Myla-RaeBaldwin]

Hello! I am adding my ArcHydro woes to a long list of troublesome and seemingly unfixable errors with the toolset! I recently upgraded from 10.3 to 10.7 and now I am having troubles with the tools in the Watershed Processing set in ArcHydro. I have read through the troubleshooting documents available and set everything up accordingly. The only thing I cannot adhere to is putting my project at the root of the C: as I do not have write privileges and I must use C:\_LOCALdata\.

I am delineating watersheds and characterizing their morphology for a number stream sampling sites. I have successfully generated the watersheds and their pour points but I have failed to run the Main Flow Path tool (I was able to in 10.3). A screenshot of the resulting error is below. Any insights would be appreciated. 

Thanks, Myla-Rae

[HaySan]

Same problems is being faced here. Though Longest Flow Path is created successfully, Main Flow Path fails and shows error no matter how I try it. I adopted all solutions suggested here to counter ArcHydro errors. Any help will be highly appreciated.