First of all, please make sure that you are on the right portal. You can only log in to the portal where you have activated your SIM card.
Here are the different portals:
Digital Republic: https://connect.digitalrepublic.ch/dr/
Pc Tipp: https://data.pctipp.ch/pctipp/
Beim einloggen wird meine eMail Adresse nicht gefunden: https://sim.conrad.ch/conrad/
Otto Fischer: https://connect.ottofischer.ch/of/
If you can't log in even on the right portal, please reset your password under "Forgot password".
If you still have difficulties, please create a support ticket.