So ive been licensed for about 3 months now (tech) and i got a baofeng uv5r to start with, yeah yeah i know, anyway. There are like 4 or 5 repeaters listed in my area on repeaterbook and i can hit two of them no problem but the other ones just dont seem to hear me at all. I can hear traffic on them fine but when i key up nothing happens. Someone at my local club mentioned something about CTCSS tones but honestly i didnt fully follow what they were saying. Is that whats going on here? Also one of the repeaters i can hit there's always these two guys having a really long conversation and i never know if im supposed to just wait or if i can break in. I dont want to be rude but also id like to actually use the thing.

yeah almost certainly a CTCSS issue. basically a lot of repeaters require you to transmit a specific sub-audible tone along with your voice, and if you dont send the right tone (or any tone at all) the repeater's controller just ignores you. it wont open up. the repeaterbook listing usually shows the tone you need under 'tone' or 'PL tone' - PL is just an old motorola trademark for the same thing. on your uv5r you have to go into the menu and set the T-CTCs (transmit tone) to whatever frequency is listed, like 100.0 or 127.3 or whatever. some repeaters are open and dont require one, which is why those two work fine without you doing anything.

as for breaking into a conversation - totally normal to feel awkward about it at first. the usual thing is to wait for a pause between transmissions and just say your callsign. like just 'W1ABC' or 'W1ABC monitoring' and they'll usually acknowledge you and you can jump in or just let them know you're around. most people are pretty welcoming about it, especially if you mention youre new.

the CTCSS thing already covered but i'll add - dont feel bad about the baofeng, half of us started on one. just program it with chirp if you havent already, doing tones through the menu manually is kind of a pain and its easy to set the wrong thing. chirp makes it a lot easier to see everything at once.

the etiquette question is a real one and honestly people dont talk about it enough. some repeaters have kind of an unwritten culture around them, like some groups are super welcoming to check-ins mid-qso and others are a bit more... cliquey i guess. if you break in and they seem annoyed just chalk it up to that particular group and try a different repeater. most hams are genuinely happy to hear a new voice though.