Update:
As per this support link... I upgrade to 4.2.1 ( https://support.gluu.org/upgrade/8887/failed-upgrade-from-420-to-421/)
but now I am getting the same error:
```
ERROR [main] [org.gluu.oxtrust.auth.uma.UmaPermissionService] (UmaPermissionService.java:109) - Failed to initialize UmaPermissionService
javax.ws.rs.NotFoundException: HTTP 404 Not Found
at org.jboss.resteasy.client.jaxrs.internal.ClientInvocation.handleErrorStatus(ClientInvocation.java:226) ~[resteasy-client-3.13.0.Final.jar:3.13.0.Final]
at org.jboss.resteasy.client.jaxrs.internal.ClientInvocation.extractResult(ClientInvocation.java:196) ~[resteasy-client-3.13.0.Final.jar:3.13.0.Final]
at org.jboss.resteasy.client.jaxrs.internal.proxy.extractors.BodyEntityExtractor.extractEntity(BodyEntityExtractor.java:62) ~[resteasy-client-3.13.0.Final.jar:3.13.0.Final]
```
```
2020-12-04 16:09:18,120 INFO [metrics-reporter-1-thread-1] [org.gluu.oxtrust.service.AppInitializer] (AppInitializer.java:316) - Created persistenceMetricEntryManager: org.gluu.persist.ldap.impl.LdapEntryManager@51da5037 with operation service: org.gluu.persist.ldap.operation.impl.LdapOperationServiceImpl@4d48b889
2020-12-04 16:11:25,681 ERROR [qtp790067787-14] [org.gluu.oxauth.client.OpenIdConfigurationClient] (OpenIdConfigurationClient.java:90) - There is an error in the JSON response. Check if there is a syntax error in the JSON response or there is a wrong key
org.json.JSONException: A JSONObject text must begin with '{' at 1 [character 2 line 1]
at org.json.JSONTokener.syntaxError(JSONTokener.java:507) ~[json-20200518.jar:?]
at org.json.JSONObject.<init>(JSONObject.java:222) ~[json-20200518.jar:?]
at org.json.JSONObject.<init>(JSONObject.java:406) ~[json-20200518.jar:?]
at org.gluu.oxauth.client.OpenIdConfigurationClient.parse(OpenIdConfigurationClient.java:112) ~[oxauth-client-4.2.1.Final.jar:?]
at org.gluu.oxauth.client.OpenIdConfigura
```