Experience with pair that doesn't seem to breed ?

Hi relatively new ard and seems like this forum actually allows ppl to discuss about breeding and stuff so here i am

I just hope tat someone actually has come across this weird situation .. and able to give me a clue as to wad's wrong ..

My pair of guinea pig just doesn't seem to breed at all . I have check their sex and determine them to be of opposite sex but the two of them just doesn't seem to breed despite being put together for like half a year LOLz .

So maybe someone can actually tell me its there actually something wrong with my gps or they just plain dun like each other ?