I suspect you don't have Mapcare and you have done a download and popped the card in ?. You said 2016 Leon is close to 2015 when models could have the Mib1 in. Worth checking the unit installed by pressing a few buttons as described on this site:
https://hereshop.navigation.com/pro...o/sku/seat_non-distro_Leon/en_GB/HEREEMEA/GBP
In 2015 the mib1 and 2 were installed. 2016 mib2.
How to identify navi version:
There are two different SEAT LEON Navigation system versions, which are externally identical. If you already know which version you have, select it from the left menu. If you want to check it, please follow these steps:
Press the “NAV” Button.
Confirm the “Setup” > “Version information” selection on the display.
Check the first text line in "Version information" with the following images:
If the first three digits are 5F0, your system version is the "Navi System - 5F0".
If the first three digits are 6P0, your system version is the "Navi System - 6P0".
On the other hand, if your system has built-in hard drive, and the first three digits are not 5F0 or 6P0, your system version is the "Navi System Plus".
If you haven't got Mapcare and it's a Mib2 Standard which will show 6P0 you have the workaround available as documented on the thread a fair few times
(see above, post 1499 is the most recent one of those).
Released June and November each year are the map updates.
See recent posts above. Post 1513 provides the most up-to-date one which covers the whole of Europe, the Seat versions haven't been update to the equivalent yet. All Mib2 Map releases whether from Seat, Skoda or VW will work in a Mib2. Note discussion round there on issues with road speeds - assume this isn't s UK based issue with the updates.
If it's a Mib1 or Navi System Plus a visit to the dealer or some other way discussed on the thread. If it has got Mapcare then it's a file presentation issue. I guess it doesn't have Mapcare.