​@Troy Tessalone I already checked the history log- Data In and Out and also shared the above screenshots with you for the error. In the step 3 no data is going out. and in step 5 it’s showing the error. 
 Please help.Thank You!
 

​@Shikha Verma 

If there is no output from Zap step 2, then there will be no output form Zap step 4, and that means Zap step 5 will have an error.

As previously suggested, you need to add Filter steps to check Zap step 3 returns a value: https://zapier.com/apps/filter/help

From the output of Zap step 2, you need to derive the first message in the thread since that will have the URL you are trying to extract in Zap step 3.

​@Shikha Verma 

If you are still having issues configuring your Zap steps, you may want to consider hiring a Certified Zapier Expert: https://zapier.com/experts

​@Troy Tessalone Yes, You are correct.
But what should i do now to achieve this?

​@Shikha Verma 

For Zap step 3, did you try mapping a variable from Zap step 2, that contains the thread message contents as previously suggested?

​@Troy Tessalone By doing some changes you suggested above and doing hit and trial, I was able to sync the comments in the right ticket. You can refer the below screenshots. 
Can you please suggest what should be in the step 6 “comment” so that it will properly sync the comments. Thanks!

​@Shikha Verma 

For Zap step 6, you would need to map the data point “Text” from Zap step 1.

Hi ​@Troy Tessalone Thank you for the information. 
I added one more step in my Zap i.e Retrieve latest thread reply and then I extract the Data/ID of that message and now the Zap is working as expected. 
Here are the below screenshot of step by step Zap. 
I really appreciate your prompt responses and sharing the information.