How to send a Base 64 post as a request?

Question

PHP

I have a picture, I get it in base 64 format. I tried to decode it
on this site , in the end everything is EXCELLENT, I get an image and see it.
I read the rucaptcha documentation at the link - link

http://rucaptcha.com/in.php?key=" . $APIKey . "&method=base64&body=" . $value . "&json=1

This is how I send them a request, the $value variable stores base64 in the format:

/9j/4AAQSkZJRgABAgAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRofHh0aHBwgJC

well, etc.. I don’t paste the whole big piece of code.
they accept my request but as a result I get an error ERROR_CAPTCHA_UNSOLVABLE
Apparently I'm doing something wrong. The picture is readable, I tried several times to send different ones, to no avail.
Can anyone tell me from experience what I'm doing wrong in the end?))