really simple captcha into contact form 7?

I have just integrated the captcha of really simple captcha into my contact form 7, but doing several tests I realize that the captcha marks all the characters entered as incorrect even if you write them well, what should it be?
I also want to know if there will be any way to integrate a captcha to contact form 7 without using plugins

• This topic was modified 7 years, 10 months ago by alberto006.