If you have no DVB-C signal, DVB-C scans will not find any services.
For DVB-T, in Tvheadend at the Configuration - DVB Inputs - TV adapters page, click on the first line showing an IP address then in the right hand pane select DVB-T as the network type and then Save the selection at the bottom.
Then check that the individual tuners are enabled by clicking on them. Amend as necessary and save any changes you make.
Edit the DVB-T network under the Networks heading and select the correct muxes. Wait until the mux scans are complete, check that all your muxes are included in the pre-defined group and map the services found.