Assuming you are using the black SmartWifi modem (Sagemcom F3896LG-ZG), a blinking red status LED directly after the initial modem startup procedure, indicates a (downstream) signal problem.
Could you post one or more pictures of the AOP (main outlet in meter cupboard or living room) and cables, plus splitter(s) and signal amplifier, as applicable?
Additionally, could you log in to the modem's web interface at 192.168.178.1 and copy the data displayed on the Downstream, Upstream and Configuration tabs on the Advanced settings, Tools, Network status page?