Where do I enable the spatial analyst extension in ArcGIS Pro?
010096: There is no Spatial Analyst license currently available or enabled.—Help | ArcGIS Desktop
This link gives information on where to check the license information for Pro.
Also, if your pro licenses have been converted to concurrent, then a license will need to be available there. If not, you organization's ArcGIS Online administrator will need to assign a license to the "named user" using the Manage Licenses in My Organization