Hey Keane!
Nice to meet you! I'm Darhyl, an Independent Advisor. I'm sorry you are experiencing this on your Minecraft account. No worries, let me help you sort this out.
Kindly try to confirm if you are using the same Microsoft account where you have purchased your Minecraft game by signing into account.microsoft.com > then go to Payment and Billing > Order History.
From there, check if you have the Minecraft game transaction. If you have found the transaction, use the same Microsoft account to log in to Minecraft Launcher.
If you haven't found the Minecraft game transaction, check your other Microsoft email accounts' Order History.
Please take your time and let me know if it works.
Best regards,
Darhyl