I dont know what tag or variable to fix in my shopify order confirmation template

I am using a shopify template and have added just a tag for first name plus, logo, buttom and couple text blocks. 

When i try to send a test it gives me the “Message displayed without tags or variablesFix invalid template tags or variables  to preview the message with actual profiles and events.”

Please help to find what to fix. 

S ome of my added texts are these:

Hi {{ first_name|default:'there' }}, 

I hope you are well today.

This email is to confirm your order on {{ date | date: "%m/%d/%Y" }}. Your order number is {{ order_number }}.

Add your tel number here so I can notify you once your order is ready for dispatch. 

I can't wait for you to get your favorites!

Kindest Regards,

Zulima V.