Cannot Create Scheduled Refresh Plan

Sometime between Sept 1 - Oct 1 2020 our server stopped allowing us to update and create scheduled refreshes on all of our reports. No Windows Updates / PowerBI Report Server updates have been applied to this server during this time period.

If we try to create a scheduled refresh plan, once we fill out the details and hit save, it throws a "An error has occurred.", Something Went Wrong. Please Try again later". The only error I can find in the PowerBI Report Server logs that correspond to the action are below (in the RSPortal log). I have found few other instances of this error on support forums and haven't been able to track down the exact cause of the issue. Any ideas?

What I've tried:

• Changing the Report Server Service Account (was "Virtual Service Account", tried "Network Service" account and a domain account w/ privileges - no success. Changed back to VSA)
• Reinstalling / repairing latest version of May 2020 Report Server and restarting server. - no success
• Tried from multiple browsers (Chrome, IE, Edge) - no success
• Downloaded PBIX file from server, re-uploaded it and tried to set scheduled refresh. - no success

2020-10-11 22:49:40.3833|INFO|4|Sending response. Response code [DOMAIN]\[user] 500, Elapsed time 0:00:00.9144013| RequestID = s_aaf174f2-e582-4ebb-90ad-db668eb35cdb 
2020-10-11 22:50:33.8839|INFO|39|Received request POST /api/v2.0/CacheRefreshPlans| RequestID = s_63ac61d5-7a79-4157-9e29-d9376b0d0d41 
2020-10-11 22:50:33.9151|ERROR|39|OData exception occurred: System.Net.WebException: The request failed with HTTP status 401: Unauthorized.
   at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.SetConnectionProtocol()
   at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.SoapMethodWrapper`1.ExecuteMethod(Boolean setConnectionProtocol)
   at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.CreateCacheRefreshPlan(String itemPath, String description, String eventType, String matchData, ParameterValue[] parameters)
   at Microsoft.ReportingServices.Portal.Services.SoapProxy.SoapRS2010Proxy.<>c__DisplayClass19_0.<CreateCacheRefreshPlan>b__0()
   at Microsoft.ReportingServices.Portal.Services.SoapProxy.SoapAuthenticationHelper.ExecuteWithWindowsAuth[TReturn](SoapHttpClientProtocol soapClient, IPrincipal userPrincipal, Func`1 func)
   at Microsoft.ReportingServices.Portal.Repositories.SubscriptionService.CreateCacheRefreshPlan(IPrincipal userPrincipal, CacheRefreshPlan cacherefreshPlan)
   at Microsoft.ReportingServices.Portal.ODataWebApi.V2.Controllers.CacheRefreshPlansController.AddEntity(CacheRefreshPlan entity)
   at Microsoft.ReportingServices.Portal.ODataWebApi.Controllers.Reflection.EntitySetReflectionODataController`1.Post(ODataPath oDataPath, T value)
   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.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_63ac61d5-7a79-4157-9e29-d9376b0d0d41 

Update: We have finally found if we use the server's "real" name to access the web portal ( ie. https://webserver.domain.com/Reports), we are able to create and modify the scheduled refresh plans again, however our alias for the server (https://iq.domain.com/Reports) is still throwing the same error.