Create hosted imagery consistently fails

[HeatherShearer55]

I am posting here, as it is a Pro issue. (ArcGIS Pro 3.7.1) I have created a mosaic dataset in Pro using the Weighted Raster Overlay toolbox (but also have tried the same using Python or  Spatial Analyst). I want to use the Create Hosted Imagery wizard to upload the WRO to ArcGIS Online and use in the Suitability Modeler Widget in Experience Builder (Developer).

However, no matter what I do (change raster type, change from dynamic to tiled, use rasters in a folder, tiff or crf, run all the sub tools in the toolbox, etc.) the wizard consistently fails, either on upload or on output. If it gets as far as upload, the error message is either the horrible Error 999999, or a variety of errors such as "Failed to submit remote task: CreateImageCollection" or "Failed to Submit Remote Task: CopyRaster". 

I have the appropriate permissions in AGOL (Professional Plus). I do not have access (yet) to ArcGIS Enterprise.

I  have done a workaround using a custom widget to dynamically change the symbology for the layers (uploaded via AGOL), but this is not ideal as is just playing with symbology.  Any help very welcome. 

[Robert_LeClair]

This behavior is most often due to Create Hosted Imagery Layer wizard limitations/bugs rather than your Weighted Raster Overlay output.

1) Confirm your mosaic dataset’s source rasters are supported by the wizard

ArcGIS Pro documentation lists a key limitation: mosaic datasets whose source rasters are in a file geodatabase or enterprise geodatabase are not supported by the Create Hosted Imagery wizard. If your mosaic references rasters inside a .gdb, the wizard can fail during the remote tasks (for example, CreateImageCollection / CopyRaster).
Source: Publish hosted imagery layers (ArcGIS Pro 3.7 docs) – Limitations

2) Known issue with the Pro wizard failing to upload/publish

There is a reported bug where the Create Hosted Imagery Layer wizard fails to upload data for tiled or dynamic imagery layers; the documented workaround is to publish from ArcGIS Online instead.
Source: BUG-000159411

3) If your failure references CopyRaster / ERROR 999999, check Parallel Processing Factor

Copy Raster can throw ERROR 999999 when Parallel Processing Factor is set to more than 1. In ArcGIS Pro, open the tool’s Environments and clear/set Parallel Processing Factor to 1 (or blank).
Source: Problem: The Copy Raster tool fails with ERROR 999999 in ArcGIS Pro

Recommended workaround (given your constraints: AGOL, no Enterprise)

Publish the output as a hosted imagery layer directly in ArcGIS Online (Content → New item → Imagery layer), rather than using the Pro wizard (this is also the workaround referenced in the bug above).