Whatsapp black bars on side of video after export

Hello,

I've never had this problem before. I was sent an Illustrator file that had about 10 elements. I exported them 4x to PNG so I can animate the Flyer on Davinci Resolve. When I export it I export it this way:

MP4
H.265
1080 x 1920
Vertical Resolution

When I open it I looks how it should but when I send it on WhatsApp it show up bars on the left and right.
ITs never happened to me before. I do this all the time so my client can approve the video. If I send the file as a file its ok when you open it but when i send it for viewing on WhatsApp it shows up like the example ive posted below. Ive rendered it in many different formats and it still shows up like that when they open it on WhatsApp

Thank you for helping me!

Ale

Weirdly enough when I export the video:

MP4
H.264
1080 x 1920
Vertical resolution

The export is perfect for WhatsApp but on the last part of the video the logo pixelates which is why I was trying to use another heavier more robust CODEC.

I've never encountered this issue before. I regularly send files for client approval by sharing them as attachments, and they typically open fine. However, when I send the same file for viewing via WhatsApp, it displays incorrectly, as shown in the example I've posted below. I've tried rendering the video in various formats, but the problem persists when opened on WhatsApp.