Layers is not getting loaded in 10.7.1

[Rutuparna_Panda]

I am getting the error "A Subscription cannot be stored unless its event class already exists." while I am trying to load charts on the Base map in ArcGIS 10.7.1 .  Layer is getting loaded in 10.6.1 but same code is not working in 10.7.1 when I change the config.esriaddinx file : 

<Targets>
<Target name="Desktop" version="10.6" />
<Target name="Desktop" version="10.7" />
</Targets>
<AddIn language="CLR" library="ArcsForGISESRI1061.dll" namespace="ArcsForGISESRI1061">

[Rutuparna_Panda · Accepted solution]

I successfully solve it. Actually the problem is in Geoserver. My Geoserver was crashed that's why the error has occurred.