You are not giving off much info....That give us a hard time to focus on a specific area.

Depending on what type of horn there can be different problems. Of course ground problems of all kinds can be a factor. Horn button or fuse connections can be oxidized. Observe there should be a fuse installed on the main wire from the battery for safety reasons. The original wiring is not fused!

Old wires broken internally or have a high resistance can be a factor. The switch on the dash can be faulty.  Depending of the horn type, worn vibrator contacts or coal brushes is another area of trouble.

Rust or stucked parts is common in horns as they are very exposed to rain and moist. As in the case with my motor horn, one of the rotor coils is broken and the horn doesn't work if the motor stops in a certain position. Hm.. that just reminded me that i have to look in to that...

By the way, if you have an original amp meter the wire is not cut in any way. There is no gain to bypass the meter as it only works off the magnetic field of the wire. I got a tip from one of the readers that for accurate reading, use only one turn and disregard that the meter says on the face "use two turns". (My bike is missing the dash so I have no meter)

Those amp.meters with cut wire does not use any more current than the Indian one as the basic function is the same, but the connections can of course loosen up or oxidize and cause high resistance. So, in reality no big gain to bypass in most cases.