I just did a quick check on IBM sample data in Oracle db and it works smoothly:

The filter in the query is "[Inventory (query)].[Time].[Quarter] in (?quarter?)" and the text prompt is set to:

I also tested it with multi-line set to "Yes". Worked also.
What datatype is your field of, where you'd like to apply the text filter?
------------------------------
Robert Dostal
Team Leader BI
GEMÜ
Ingelfingen
------------------------------
Original Message:
Sent: Fri January 07, 2022 06:00 AM
From: Priyanka Joshi
Subject: Text box prompt
Yes I am using in operator.
------------------------------
Priyanka Joshi
------------------------------
Original Message:
Sent: Fri January 07, 2022 04:25 AM
From: Chris Turner
Subject: Text box prompt
Obvious thing first - is your filter something like [YourDataField] in ?YourPrompt? rather than [YourDataField] = ?YourPrompt?
------------------------------
Chris Turner