If your TikTok pixels are Shopify pixels, they are not yet available for the Events API. You need to create the pixel manually on TikTok Ads Manager. 

Step 1: Go to your TikTok Ads Manager and login to your ad account
Select Assets and choose Event

Step 2: On Website Pixel and click on Manage
Choose Create Pixel

Step 3: Name the pixel and select Manually Install pixel code

Step 4: Choose Developer Mode

Step 5: Copy the pixel code and paste it into our app