OSError when using arcpy.mp.ArcGISProject()

[MM598]

I am trying to zoom into a selected polygon as part of code for a custom print tool within AppBuilder. Below is my code. However, I am having trouble getting it to zoom into the selected polygon. I have ran into various errors, but the current error is below. Any ideas for resolving this?

Code:

# Part 3: Zoom into selected polygon

aprx = arcpy.mp.ArcGISProject("CURRENT")

# trying to zoom into sltPoly
mv = aprx.activeView # mapview
m = mv.map # map
lay = m.listLayers(sltPoly)
sltLyr = m.listLayers()[3]
for g in m.listLayers():
    print("Layer: {0} Layers".format(g.name))
lyrExt = mv.getLayerExtent(sltLyr)
mv.camera.setExtent(lyrExt)
df.scale = 6000
arcpy.SelectLayerByAttribute_management(sltPoly, "CLEAR_SELECTION")
arcpy.Near_analysis(points_lyr, sltPoly)

Error (redacting was my own):

Error executing tool. Export Web Map : Traceback (most recent call last): File "**redacted**\dynamicprintservice\ExportWebMap.py", line 211, in <module> aprx = arcpy.mp.ArcGISProject("CURRENT") File "c:\program files\arcgis\server\framework\runtime\arcgis\Resources\arcpy\arcpy\_mp.py", line 337, in __init__ self._arc_object = arcgisscripting._mapping.ArcGISProject(*gp_fixargs((aprx_path,), True)) OSError: CURRENT Failed to execute (Export Web Map). Failed to execute (Export Web Map).

[DanPatterson]

related

Solved: Why does arcpy.mp.ArcGISProject() give an OSError? - Esri Community

CURRENT can only be used from an open project and python being able to see the project (eg a custom or python tool in a toolbox, or the python IDE etc)

[MM598]

I did come across that thread, but it did not seem related because I am not referring to a toolbox as this user was in their code. 

I actually am running the tool within an app with an open map via a print tool, so python "seeing" the project should not be a problem.

[DanPatterson]

might be the case, but you could check by throwing in an arcpy.AddMessage and/or print statement after getting it... perhaps

aprx = arcpy.mp.ArcGISProject("CURRENT")

print(aprx.filePath)

[gh8reth]

related

I too am having problems with arcpy.mp.ArcGISProject("CURRENT")

As part of my code I use arcpy.mp.ArcGISProject("CURRENT") to detect whether a script is running within ArcGIS Pro or outside (i.e. from IDE or scheduled task).  I notice that occasionally  arcpy.mp.ArcGISProject("CURRENT")  throws an OSError  which is caught by a try ... except, despite running the script as a Python toolbox. 

This will happen a couple of times, and then ArcGIS Pro will revert to its expected behaviour.