Hello @Simoncmo 

Thank you for reaching out to us and welcome to the TP-Link community.

If the router behaves like that, please check the below suggestions and proceed: 
1. Please be sure you are using the original power adapter, which should be 12 V ⎓ 5 A.
2. If possible and to make sure this is not an adapter issue, you may try another power adapter with the same power specification.
3. Try to reset it by holding the reset button for 10s or longer to see if it will change anything.
4. Is there any power outage/bad weather before it behaves like this?

If nothing helps, it's suggested to contact the local tech support, so they can work with you in looking into the issue further or help with the replacement:
https://www.tp-link.com/support/contact-technical-support/#Hotline-Support