Guy friend suddenly gone cold?

My guy friend who I am close to at work, who uses pet names suddenly overnight went cold, he has been up and down for couple of months. His girlfriend doesn’t like me but this has been for years. sexual stuff happened few years back. She don’t know.

Tuesday I was A/L from work at London with my sick dad, he message saying “miss the queen steak (my nickname he calls me steak of the office) saying deeply miss you. Hehe

Left a voice note saying hoped I was ok etc and office be steakless without me.

So Thursday comes in the office, he msgs teams really cold, very serious formal saying business pup. Pup is him.

I ask what’s up. He says not lunching no more I am bottom of pile smirking at me. The day after at home I message on teams saying what’s up, he goes “steak chat boring” 😓😓 but why the sad emoji did he put after?

he goes rather lunch with guys now if honest and why do I want to be mates with him he hardly been a good friend 🤣🤣

I don’t get it at all like what the hell. He has been so up and down.
it’s so hurtful. Downplaying msgs our friendship so sudden then later he slips and says steak pup meaning him l, but won’t answer any of my questions , just says have chat Tuesday canteen but nothing I done😓

He did say sorry mentioned before chit chat on msgs don’t like really have told you thus before , which he did 3 months ago for no reason, he says new direction and Turing 30, but then he chases again when I pull away. Back to this again but if about msgs , why saying no lunch nothing?

it’s really upset me why would he do this?

Updates
10 mo
I guess why would a guy do this so sudden again, could it be his girlfriend saw something, if so why not say, he says busy with new buisness outside of work, but why would that make him go like that.
To add on the day after he said “ Missed me deeply” I said aww loved that message, he says another guy made me type it. Which was weird to say, he typed it.

Also he use to be very emotional, show so much more care in msgs, now more bants
Guy friend suddenly gone cold?
Post Opinion