Join form does not work

I have a problem with my join field. User will click on join now on my site, then the join form will come up. User will then fill out everything and upload a photo, then click Join Now. Then a red circle appears next to Join NOw, but will not tell you what the error is. I need someone to fix this error ASAP. Please only contact me if you have knowledge on how to fix this field. If you do not know how to fix this right off  the back then please do not waist my time by replying to this job. Thanks.