Which version of Tvheadend are you using and is it self-built or are you using a package? If packaged where did it come from?
It now seems that the scan tables are built into the Tvheadend package on some (most?) distributions so cannot officially be updated separately.
As an unofficial workaround (tested OK) if you are using a package and cannot get a recent update
cd /usr/share/tvheadend/data/
git clone https://github.com/tvheadend/dtv-scan-tables.git
mv dvb-scan dvb-scan.old
mv dtv-scan-tables dvb-scan
I can now see the new muxes in the 'add new network' box, though for some reason without the country.