If it said "Mysterious forces prevented you from opening that portal. Please try another location", then there isn't a suitable portal destination for that location and you should try opening a portal at another location.
Reasons for there being no suitable destination location are usually quite extreme, for example the entire area around the destination might be protected/owned by someone else down to a deep depth, or be full of structures that people have built. But those two scenarios seem unlikely unless you're already in the nether and trying to open a portal to the surface where there's a big city or something.
If it actually said "Nether portal fails to open", then this probably isn't the same nether mod as the one you have installed, because there isn't any text like that inside this mod.
If you put the details into the issue tracker it can probably be solved. Include where you were when you tried to activate the portal and which game you are playing, what other mods are loaded (a mod might be why the area is blocked), and the wording of the "portal fails to open" message.