Unable to manage or create subscriptions in Web Portal

THis is what I find in the RSPortal_YYYY_MM_DD_HH_MM_SS.log file:

2022-08-02 15:02:37.4765|ERROR|11|OData exception occurred: System.Net.WebException: The request failed with HTTP status 503: Service Unavailable.
at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
at Microsoft.SqlServer.ReportingServices2010.ReportingService2010.GetItemParameters(String ItemPath, String HistoryID, Boolean ForRendering, ParameterValue[] Values, DataSourceCredentials[] Credentials)
at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.<>c__DisplayClass94_0.<GetItemParameters>b__0()
at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.SoapMethodWrapper`1.ExecuteMethod(Boolean setConnectionProtocol)
at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.GetItemParameters(String itemPath, String historyId, Boolean forRendering, ParameterValue[] values, DataSourceCredentials[] credentials)
at Microsoft.ReportingServices.Portal.Services.SoapProxy.SoapRS2010Proxy.<>c__DisplayClass6_0.<GetItemParameters>b__0()
at Microsoft.ReportingServices.Portal.Services.SoapProxy.SoapAuthenticationHelper.ExecuteWithWindowsAuth[TReturn](SoapHttpClientProtocol soapClient, IPrincipal userPrincipal, Func`1 func)
at Microsoft.ReportingServices.Portal.Services.SoapProxy.SoapRS2010Proxy.GetParameterTypes(IPrincipal userPrincipal, String reportpath)
at Microsoft.ReportingServices.Portal.Repositories.SubscriptionService.<>c__DisplayClass4_0.<GetSubscriptions>b__0(SubscriptionImpl x)
at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at Microsoft.ReportingServices.Portal.ODataWebApi.V1.Controllers.SubscriptionsController.GetEntitySet(String castName)
at Microsoft.ReportingServices.Portal.ODataWebApi.Controllers.Reflection.EntitySetReflectionODataController`1.GetRoot(ODataPath oDataPath, Int32& index)
at Microsoft.ReportingServices.Portal.ODataWebApi.Controllers.Reflection.ReflectionODataController`1.Get(ODataPath oDataPath)
at lambda_method(Closure , Object , Object[] )
at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass6_2.<GetExecutor>b__2(Object instance, Object[] methodParameters)
at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__6.MoveNext().| RequestID = s_3d76d1b9-c25a-45e5-a52a-5b065155f1ed