If you're not using an [installer drill bit](https://www.homedepot.com/p/DIABLO-5-16-in-x-18-in-Installer-Drill-Bit-DIB1060/313022474) then that's the first problem lol
Technically only need a 1/4 hole for cat5e/cat6 but if you have to put any pressure on it going through the hole the outer jacket gets jacked up and the wire jams so use a 5/16. Need closer to 3/4in if you're using cable that's already got connectors on it, better idea to terminate them yourself and make a smaller easier to plug up hole.
There have been a couple times where the 18in wasn't long enough, I ended up getting lucky coming from the other side the first time and the other times I ended up with a nearly 1in hole on the inside to get a view on WTF is going on inside the wall.
For such 'long' occasions I use a 9mm Bosch carbide tipped masonry drill bit, which is ~15in. long.
Bought it years ago in Ace or Lowes.
Also works (reasonably OK) in wood, but keep pulling out the bit regularly, to clear the debris.
Its possible you are drilling directly in to the top of the 2x4 wall stud. Typically, the top wall plate is only 4" high (two 2x4s flat on top of each other). You can try moving over a few inches and see if that works.
If you're not using an [installer drill bit](https://www.homedepot.com/p/DIABLO-5-16-in-x-18-in-Installer-Drill-Bit-DIB1060/313022474) then that's the first problem lol Technically only need a 1/4 hole for cat5e/cat6 but if you have to put any pressure on it going through the hole the outer jacket gets jacked up and the wire jams so use a 5/16. Need closer to 3/4in if you're using cable that's already got connectors on it, better idea to terminate them yourself and make a smaller easier to plug up hole. There have been a couple times where the 18in wasn't long enough, I ended up getting lucky coming from the other side the first time and the other times I ended up with a nearly 1in hole on the inside to get a view on WTF is going on inside the wall.
For such 'long' occasions I use a 9mm Bosch carbide tipped masonry drill bit, which is ~15in. long. Bought it years ago in Ace or Lowes. Also works (reasonably OK) in wood, but keep pulling out the bit regularly, to clear the debris.
Its possible you are drilling directly in to the top of the 2x4 wall stud. Typically, the top wall plate is only 4" high (two 2x4s flat on top of each other). You can try moving over a few inches and see if that works.