No error message, no attachment uploaded… This is what I got when I tried to upload file that size more than 8 MB to phpBB lately. How to fix phpBB fails to upload large size file? Simple. Just create php.ini file. And put these in.
memory_limit = 100000000
post_max_size = 20m
upload_max_filesize = 20m
Upload php.ini to your hosting root. That’s all.