UPDATE 2:
I booked my flight at https://www.edreams.net/ . I contacted them to sort out how to fix my flights, The response was to contact the airlines directly and work with them. However, edreams.net provided me no ticket number, so the airlines cannot help me. What a mess...
Think at this point I am out the $150 for the Covid test and the cost of the flight. What a bad way to end a day. :/ Going to sleep now.
Sorry to hear about it Tim. Tedreams is suck. That's one of the reasons why I don't like to book through agencies. I hope they will fix it for you. I believe VN Govt going to open the border very soon and hope to see you in VN again.
Stay safe and take care