No user manual for the Sercomm S3 AC2100 mentions this, but if the Power light blinks amber continuously for more than 5 minutes, the router is stuck in a boot loop – see the Troubleshooting section below.
Before diving into configuration, let’s understand what the Sercomm S3 AC2100 is capable of. The "AC2100" designation refers to the combined theoretical throughput of both frequency bands. Sercomm S3 Ac2100 Router Manual