I am in the process of using approximately 20 TIFF's of aerial imagery, taken from a drone flyover, for a combined JPG of them all, stitched together in GlobalMapper. The JPG saves fine in GlobalMapper, and once it is saved I reprojected it to the NZTM coordinate system, which is what our ArcGIS Pro projects and Web Maps are in. I brought the reprojected JPG into ArcGIS Pro, defined it's projection to NZTM as it had 'Unknown Coordinate System' in the 'Spatial Reference' section of the properties, and it was displaying fine in Pro at that point. I then start the process of uploading it to ArcGIS Online, as I wanted to use the combined JPG in a web map; the layer type was set to Tile, the folders and Online groups were assigned, the tiling scheme was selected to be 'Existing cached map/image service' and used a layer that we knew to be NZTM also. The level of detail was the full range: 0 to 17 zoom levels. It was cached locally on my computer's hard drive, and the 'Allow clients to export cache tiles' button was ticked. There were no errors that popped up when 'Analyse' was clicked, so there was nothing to suggest anything out of the ordinary. However, when I went to publish the layer, the tile package was created then it began building the tile, at which point the error 'Failed to cook tiles' appeared, with no error code or any further information. Has anyone else experienced this issue and can shed some light on what is going wrong + why? I have tried multiple caching locations and multiple zoom levels with no differing results.