Samknows like other speed testing sites cannot be relied upon alone. They all have their bad days, partly due to their own websitesite issues and the particular internet server they decide to use in their test. You must compare to other sites !. We often find samknows doesn't work at all with a variety of unhelpful error messages.
It's important to understand what each site is actually measuring too. Some measure speed to the hub/modem, others the speed to your actual device. Hence results can be considerably different and affected by your connection method too.
On your mobile ?, so you're using WiFi. Do you have WiFi5, WiFi6 or the old 2.5 WiFi ?, all quite different in speed capability. Are you near to the hub with nothing between you or through walls and doors ?. Is your hub hidden in the furthest corner of the house or central and off the floor ?
Connected via ethernet ?. Direct to your pc ?, cat 5e or 6a ?. If you have a hub5 are you using the 2.5gb socket or one of the 1gb sockets and what is the ethernet of your pc capable of ?. There is also the performance of your pc to consider, your processor, the hard drive. So much can affect your speed results.
Sites to try....
https://www.broadbandspeedtest.org.uk/
https://www.speedtest.net/
https://www.samknows.com/realspeed/
https://fast.com/#
