Sorry, you've reached your maximum limit of Lightsail Instances

You can request quota increases if your usage within a region exceeds the Lightsail quotas. https://docs.aws.amazon.com/general/latest/gr/lightsail.html .

I have the same issue, but I am unable to contact customer support as I'm on the Free Tier. Is there anything I can do?

You can contact AWS Support regarding account-related matters and costs.

Please contact AWS Support by opening a case under "Account and billing" to increase limit. https://docs.aws.amazon.com/awssupport/latest/user/case-management.html