I just got same error report
I had never gotten such error before and so decided to check if anyone's had made same complains before then I saw yours. I tried uploading same image again but this time I edited image image from png(2.45mb) to jpeg(1mb) and it worked. I would suggest you do same mate. I don't know if it will work though for you. Please, I would love if someone could explain why this is happening because the image size limit for Talking.com is 2.5mb and my image didn't exceed this limit.
Well you are right I just tried to upload different png files with size 2.48mb, 2.46mb. 2.38mb, they all failed gave File Size error on client side.
I know this is error is on the client side since talkimg is checking image size on the client, before sending data to server.
However when I reduced the file size to 2.32mb, 2.2mb and 2.0mb i didn't get the error on client side but after I click upload got the same below error.
In the mean time i noticed my image size was <2.5mb but image dimension were above 1800x1800 pixels. When I reduced the dimension to 1700x1700 pixels, file was uploaded successfully.
I think joker_josue can answer this, however it looks like not only the image size but image dimensions or may be some other checks are in place which prevents upload on the server size.
Edit: I think my image dimension theory is wrong since I'm able to upload large 2200x2200 pixels image with smaller file size of 1.6mb.
But yes above error is valid and is reproduced able.
Edit 2:All my above work goes in vain, just click "Check the error report" link and it says
So in simple words file size must be 2mb not 2.5mb