Public archives have cataloged specific dump files for this model and its chassis (TP.MS1306.PB775):
(2.3 MB) — Standard flash dump for the L40D2900 model. Download FLASH DUMP TCL L40D2900 rar
Press and hold the on the TV (not the remote). Public archives have cataloged specific dump files for
While holding the button, plug the TV back in or power it on. Continue holding for about until the upgrade screen appears. The process takes approximately 4 minutes to complete. Official Support Channels Continue holding for about until the upgrade screen appears
Because TCL’s website does not always provide public download links for these specific bin files, it is recommended to contact the TCL after-sales team if the community files do not work. They can often provide a direct link to the correct software based on your serial number.
If your TV is still functional enough to access the boot sequence, you can attempt a local update: to FAT32.
— Often used for cross-compatible chassis versions.