The first checks to make are to see if the router lights are on and green. If they are not, you should check that all cables are properly connected, with no bent parts, and reboot your router.
Depending on the state of the lights on your router, the stability of your connection may vary. To check if it is an issue, you can call (+34) 951 238 600 or contact the support team by sending an email to soporte@axartel.es.