Creating Accuracy Assessment Points gives Error 999999 in ArcGIS Desktop?

I am using ArcGIS Desktop 10.6.1.

I am trying to create 500 stratified random accuracy assessment points for my raster generated using the supervised classification tool (followed by the reclassify tool to combine multiple agricultural classes into a single value). I open the “Create Accuracy Assessment Points” tool, select my reclassified raster, specify a name and file geodatabase for the output, and leave the default settings for the other parameters (Classified target field, 500 points, Stratified_Random Sampling strategy).

I then get a failed analysis, and under Results: Messages, it states, “Error 999999: Error executing function.” and “Failed to execute (CreateAccuracyAssessmentPoints). The ESRI help page offers two possible reasons for this: the input file does not contain an integer field with the name “Value,” or you try to use the Stratified Random sampling strategy with a class that has a count of less than 10 pixels. I verified that I do have a field in my attribute table named “Value” with the “Long integer” class. I also checked the counts- none of my five values have pixel counts less than ~55,000.

To try to identify what the problem might be, I tried running the analysis with a Random sampling strategy instead, but got the same error. I also tried creating a new map document, resetting the only environment variables that I had adjusted (processing extent, snap raster, and raster mask), and processing a different classified raster. I get the same error each time.

Does anyone have ideas on what might be causing the problem, or even other ways that I might troubleshoot this particular analysis?