That must be some old / not current flight plan, as these airways do not link those waypoints (which you can see in the map itself - check the airway labels).
The area is a bit cluttered, but there is a function to search the map visually. Right click on the map between SEBON and IKLOK. In the list, select UJ18 (the one in your flight plan). As you can see in the list of segments to the right, IKLOK links to ZARCO (east of SEBON) and not SEBON. You can also see this visually by the fact that the airway line passes through SEBON - you can tell that an airway and a waypoint are linked if the airway line stops just outside of the waypoint symbol.
Then, after IKLOK, you have UT23 in your flight plan, but the airway name is UT123 as you can see:
Hence, the full route should be (paste in the Type route window):
MMMX DCT ZARCO UJ18 IKLOK UT123 ULUVO DCT GDL DCT MMGL
(Although a shorter route might be:)
MMMX DCT TLC UJ12 GDL DCT MMGL