The problem is, your text was about a professional issue, so he responded in a professional way. I couldn’t really see him responding something ‘flirty’ in that situation. If you had texted something like ‘I’m trying to bring my walls down because i really like you and want to get to know you better’ and then he texted ‘nice thanks!’ ... personally i still wouldn’t say that shows disinterest, but i would understand more why you would possibly mean it does. His response was perfectly acceptable for the original message you texted him. There was nothing to indicate you like him, so you cant say his response shows disinterest. Perhaps he didn’t feel like going into more detail as use two have already cleared up the misunderstanding.
But overall, I’m still shocked in 2019 people still do not have the courage to tell someone they like them. It’s really not that hard to ask someone if they want to go for a drink or go to dinner or something. If they say no, or say sorry I’m not interested then it ok. Get over it and they’ve saved you wasting more time pining over them when you could be pursuing someone who is interested. Also if you never directly say you’re interested, they may never know and end up with someone else. Not everyone is good at picking up the signs. The best thing to do is always be direct.