It can take up to 40 minutes to activate a subscription plan in the account.
Make sure you submitted your payment from your account or used the registered email address while checking out from the Plans & Pricing page. If you buy a plan from the Plans & Pricing page and use a different email (not the same one you used during registering), a new account will be created in the system. The login credentials will be sent to the email which was used for making payments from SE Ranking.
Please contact our support team, if you want to transfer the plan from the newly created account to the one you initially registered.