On changing the status reason to cancelled , the error Message "Invalid Status Reason for a Task Status of Closed. (ARERR 45098)".

The below could be seen on the Active Link Logs.

<ACTL> Checking TMS:SHR:SetStatusReasonSelection (0)
<ACTL>     -> Passed qualification -- perform if actions
<ACTL>          0: Set Fields

<ACTL>             Status Reason Selection (10003018) = ""

The Status Reason Selection Value was being Set to Null

This knowledge article may contain information that does not apply to version 21.05 or later which runs in a container environment. Please refer to Article Number 000385088 for more information about troubleshooting BMC products in containers.

• Follow the below steps to Identify and Fix the issue.
• From the Midtier , Open SYS:Status Reason Menu Items form and enter the Below Value

Form Name: TMS:Task
Character Field Value: Closed

Perform the search.

Validate the entry for the Cancelled Status. If there is a mismatch in the entry make Changes to the same.

• Open the TMS:Task Form from the Developer Studio
• Open the Outline and look for StatusReasonSelection 

Correct the alias from "Canceled" to correct alias value "Cancelled" on TMS:Task (customized view) for field "StatusReasonSelection" Field ID: 10003018

• Validate the Selections 
• Here the Cancelled Status had a mismatch in the Spelling on the Alias Column, causing the issue.
• Save the Changes and Flush Midtier Cache and test the same again.