I have faced the same issue. I have tried to upload the bin file and upgrade the firmware version. Process End up with " Error code: 4503 The uploaded file was not accepted."
My Hardware version - Archer MR200 v4 00000001
current firmware version - 1.0.0 0.9.1 v0001.0 Build 190603 Rel.60023n
I need to upgrade the firmware to the newest one of V4 that was Published on 2020-06-28.
URL that I have downloaded the firmware - https://www.tp-link.com/in/support/download/archer-mr200/v4/#Firmware
Reason for upgrading the firmware - after I changed the wifi access password and router, it will successfully change to a new one. But when I trying to reboot the router it blinks power led only. that is the issue. after I have reset the router using the reset button and router worked finely.
I have reset to the factory settings and did the firmware upgrade again. Same Result occured.
Used browsers - Microsoft Edge, Google Chrome, FireFox