Sorry man, but that happens because tabby is correct: achievements are broken. Originally people should've received them when they were awarded, but somewhere along the line, something happened that broke achievements (probably a new feature that isn't compatible with them)
Most achievements won't work, such as full sets of anything, anything that requires a number (50 acid bloods may or may not work) and any achievements that require you to win a certain amount of anything. Those ones are the most broken and have a low chance of working when you achieve them