Roblox might not be letting you log in due to several reasons. One common issue is that the Roblox servers may be down. When this happens, you need to wait a few hours before trying to log in again.
Another possible reason is captcha issues. Make sure your internet settings allow the domains `*.arkoselabs.com` and `*.funcaptcha.com` to prevent blocking the captcha.
Browser extensions can also cause login problems. Disable any ad blockers and VPNs, as they may interfere with the login process. Trying to log in from a private browser tab can also help.
Clearing your temporary internet files and cookies can often resolve login issues. This is a simple step that can make a big difference.
If none of these solutions work, your account might be restricted by Roblox due to guideline violations or suspicious activity. In this case, contact Roblox support for help.