You will only have an account if you have purchased any graphics on the site within the last 3 years. The platinum is a separate account and not linked to the home page store.
If you are wanting to purchase graphics then you can make a new account at checkout. You can use the same email and password as your platinum account if you want. The accounts won’t be linked to each other but can have the same email.
If you are just trying to look up an older perpetual license key from 3+ years again then you don’t need to login. The older keys are not linked to any accounts on the new website. However, there is a lookup page here. You don’t need an account. You just enter the email and it will send you any older keys. Make sure to check the spam inbox too because these email are sent directly from the server php which tends to trigger the spam inbox since they are not routed through an email provider service.