Slack Blocks with Zapeir reply as thread

Hi 

I am currently working on sending custom-formatted messages to Slack using Slack blocks via Zapier webhooks. I chose this approach because the native Zapier Slack app only sends the blocks as plain text, which doesn't meet my requirements.

Here are the specific steps I've taken:

1. Slack blocks are formated by code by zapier
2. Zapier Webhooks: I set up a webhook in Zapier to send a Slack message with blocks. The blocks include nicely formatted text and images.
3. Threading Issue: I need these messages to appear as replies in a thread. To achieve this, I included the thread_ts with ts value parameter in the initial data field and also tried adding it as a header. Message is still sent into channel not as a reply