*Posting this info in the hope that it helps others*

I have 2x TP-Link EAP245 Ver. 3 with firmware [5.0.1 Build 20210113 Rel. 63140(4a50)]

Whenever I attempted to update the firmware, I got the message "Bad file" or "Failed to check for new update".

Reading other posts on here/the web, I tried the UK (EU), US and CA firmware downloads, but get the same messages.

After a few days of banging my head against a virtual brick wall, I was finally able to identify the issue:

Although my hardware stated (EU) region, and all material (including the box) was all in English language. A small sticker on the retail/external packaging/box, stated "support.jp@tp-link.com" - identifying the unit as "Region = Japan", although everything was in English, I tried, and successfully updated both of my EAP245 v3 with firmware [EAP245(JP)_V3_5.0.5 Build 20220323]

Upon inspection of the JP firmware site for V3, I also found the matching [5.0.1 Build 20210113 Rel. 63140(4a50)]

Link to the JP firmware download page (use Google Translate to translate the entire page): https://www.tp-link.com/jp/support/download/eap245/v3/#Firmware

Thought I'd share this in the hope that'll help others