Instance of workspace item with type "Terrasoft.Configuration.TgAcceptanceCoverageAndObjectSchema" cannot be obtained from server metadata

Hello everyone,

i got some trouble here and the message is :

Server Error in '/0' Application.
Instance of workspace item with type "Terrasoft.Configuration.TgAcceptanceCoverageAndObjectSchema" cannot be obtained from server metadata
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
 
Exception Details: Terrasoft.Common.NullOrEmptyException: Instance of workspace item with type "Terrasoft.Configuration.TgAcceptanceCoverageAndObjectSchema" cannot be obtained from server metadata
 
Source Error:
 
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
 
Stack Trace:
 
 
[NullOrEmptyException: Instance of workspace item with type "Terrasoft.Configuration.TgAcceptanceCoverageAndObjectSchema" cannot be obtained from server metadata]
   Terrasoft.Core.Entities.EntitySchemaManager.InitializeSchema(ISchemaManagerItem schemaManagerItem, Assembly assembly) +221
   Terrasoft.Core.SchemaManagerItem`1.get_Instance() +208
   Terrasoft.Core.Manager`2.GetInstanceByUId(Guid uid) +96
   Terrasoft.Configuration.ConfigurationSectionHelper.InnerGetEntitiesStructure(UserConnection userConnection, IEnumerable`1 entityNames) +4871
   Terrasoft.Configuration.ConfigurationSectionHelper.GetConfigurationStructuresScripts(UserConnection userConnection) +80
   Terrasoft.Configuration.ConfigurationSectionHelper.GetConfigurationScript(UserConnection userConnection) +202
   Terrasoft.WebApp.Nui.ViewModuleHelper.CreateModulesConfigScript(UserConnection userConnection, HttpResponseBase response) +160
   Terrasoft.WebApp.Nui.ViewModule.SetupModulesConfig() +76
   Terrasoft.WebApp.Nui.ViewModule.Page_Load(Object sender, EventArgs e) +171
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +154
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4082

Do you have any idea guys for solve this error? thank you