@SriRaghavendran Prabhakaran Thanks for posting your question in Microsoft Q&A, apologize for any inconvenience caused on this.
In Append to Array variable action try adding another parameter with contentType
as shown below in the similar thread here.
[{ "ContentType": "Content type", "ContentData": "Content data" }, { "ContentType": "Content type", "ContentData": "Content data" }]
If you are still facing the issue, help us with the error message and actions involved in your workflow.