First of all, please make sure that you are on the right portal. You must activate the SIM card where you bought it.
Digital Republic: https://connect.digitalrepublic.ch/dr/
Digitec: https://iot.digitec.ch/digitec/
Pc Tip: https://data.pctipp.ch/pctipp/
Conrad: https://sim.conrad.ch/conrad/
Otto Fischer: https://connect.ottofischer.ch/of/
Please enter the SIM ICCID number without any spaces.