Cannot Create ArcHydro AddIn

[RobertStevens]

I am using arcgis Pro 3.1

I am experienced with arcgis Pro, but not at all familiar with ArcHydro. I have the .msi download from the archydro resources website, the 3.5.0 version. I have installed this software

My understanding is that this software must be added to arcgis pro. I use pro's Add-In Manager:
Add-In Manager => Options => Add Folder (Load all Add-Ins without restriction is set)
and this brings up a browse window. But this browse window does not list C:\ProgramData which is where the .esriAddInX file for ArcHydro is located. Why not?? Thus I am unable to load the Add-In.

Am I correct in thinking that ArcHydro needs to be loaded as an Add-In?? Regardless of my lack of understanding of ArcHydro I do not at all understand why the browser window does not display under C:
the ProgramData subdirectory (it does, for example display Program Files)

[DeanDjokic · Accepted solution]

You should not have to do anything after running Arc Hydro install .msi (assuming it successfully installed).  The Arc Hydro add-in should just "appear" next time you open Pro and so should the Arc Hydro Pro toolbox.  If it does not, try to uninstall it (using Windows Add/Remove Programs) and then installing it again.  Make sure that all instances of ArcGIS Pro are closed before you do uninstall/install.  You will need admin rights for installing.

[RobertStevens]

Ty for the response.

[RaymondCrew]

I was having a very similar problem. My org runs Pro version 3.1.3. (3.1.41833) I installed Hydro 3.1.73 and Graip Lite 3.1.73 and it would not load. Turns out changing the Registry setting about which Add Ins to load was the key for me. By default, it was set to #2, Esri signed Add Ins only. Changing it from 2 to 1 (any signed Add In) still did not allow Hydro or Graip, it did however allow another Add In I was troubleshooting, Eagle View, to run.

I then changed the value to zero, allow all Add Ins. That has now allowed Hydro and Graip to work. Find it disturbing that Esri has failed to properly include a certificate with Hydro. 

Resource on the Registry changes I had to make:
ArcGIS Pro Registry Keys · Esri/arcgis-pro-sdk Wiki · GitHub