When saving a layer as an offline service definition file in ArcGIS Pro, the "Failed to load tiling scheme from file..." message is returned when selecting a valid Tiling Scheme that is not the default.
In ArcGIS Pro, on the Contents pane, right-click a raster or vector layer. This does not have to be the layer intended to be used to create the final offline service definition file, assuming all of the steps of this workaround are followed.
In the drop-down list, navigate to Sharing, and select Save As Offline Service Definition.
In the Save As Offline Service Definition pane, on the General tab, complete the Name, Summary, and Tag fields. For Version, select an ArcGIS Enterprise version. This issue is reproducible regardless of which ArcGIS Enterprise version is selected. However, do not select the ArcGIS Online option as a version since the workflow is not reproducible if that option is selected.
Click the Configuration tab.
On the Configuration tab. under Layer(s), click the pencil icon next to Map Image. This opens the Map Image Properties page.
Under Map Image Properties, under Layer Drawing, select 'Using tiles from a new cache'. A Tiling Scheme section appears under Layer Drawing.
In the Tiling Scheme drop-down list, there is a default option and this default option is depended on what the selected layer being saved as an offline service definition file is. Leave the Tiling Scheme drop-down list at the default option.
At the bottom of the Save As Offline Service Definition pane, under Finish Staging, click Analyze. If no warning or errors appear, under Finish Staging, click Save. In the Save As Service Definition File dialog box, choose a name and location to save the output offline service definition file (.sd), and then click Save.
Assuming that the intended Tiling Scheme to use when creating the offline service definition file is set as the default, ensure ArcGIS Pro is open and not closed out of the Save As Offline Service Definition pane.
On the Contents pane, right-click a raster or vector layer. This should be the layer intended to be used to create the final offline service definition file.
In the drop-down list, navigate to Sharing, and select Save As Offline Service Definition.
In the Save As Offline Service Definition pane, on the General tab, complete the Name, Summary, and Tags fields. Under Version, select an ArcGIS Enterprise version. This issue is reproducible regardless of which ArcGIS Enterprise version is selected. However, do not select the ArcGIS Online option as a version since the workflow is not reproducible if that option is selected.
Click the Configuration tab.
On the Configuration tab, under Layer(s), click the pencil icon next to Map Image. This opens the Map Image Properties page.
Under Map Image Properties, under Layer Drawing, select 'Using tiles from a new cache'. A Tiling Scheme section appears under Layer Drawing.
In the Tiling Scheme drop-down list, there is a default option and this default option is depended on what the selected layer being saved as an offline service definition file is. Select any option from the Tiling Scheme drop-down list, and there should be no errors when selecting any options, including the 'Tiling scheme file' or the 'Existing cached map / image service' options. Thus there is no further issues with creating an offline service definition file with the intended tiling scheme.