If Snapchat is not letting you accept friends, there are a few possible reasons for this. It is possible that your account has been temporarily locked due to suspicious activity, in which case you will need to verify your account by completing a captcha. It is also possible that you have reached the maximum number of friends allowed on Snapchat, which is 2,000.
If this is the case, you will need to remove some of your current friends in order to add new ones. Additionally, if you are trying to add a large number of friends at once, Snapchat may temporarily block you from adding more friends in order to prevent spam. If you are still having trouble adding friends on Snapchat, you can contact Snapchat support for assistance.