If you are unable to login, there may be several reasons. 

1. Check the internet connection. If using Wi-Fi only, be sure the firewall is not blocking PubSafe traffic. Disable Wi-Fi and enable a cellular service, and try again. 
2. Duplicate email. An email can only be used once. If you join multiple organizations, you can switch between organizations with the same email by switching the organization in the app under the More menu.
3. Incorrect password. Use the password reset function and try again. 
4. Membership. You may not be an approved member of an organization. Approving an invitation is not the final step. An org admin must confirm your membership. This is a security feature since QR codes and emails links can be shared once distributed.
5. Blocked. PubSafe may have blocked your email for going against the use policy and community standards.