Direct Connect has always been a thing of luck to succeed with.
The person might not have been online at time you tried to direct connect to them. Else all their upload slots used up & bandwidth mostly used up preventing a successful DC. Another possibility is a high % of people have dynamic ip addresses, thus their ip address today might be different to what it was before.

Likewise I made notes on ip addresses to DC. I occasionally found same host & noticed they used at least 4 ip addresses they would rotate around. I was unable to find the others so was not always able to DC with them.

Browse host suffers some similar problems. It is not a highly reliable tool. Even harder from upload window. If the other person has non-configured firewall then DC will not succeed & browse host often does not succeed. Browse host is easier to succeed with 'if' the other person has Chat enabled. This seems to open up a channel that Browse host & DC seem to work easier through. So right-click the heading bar on your download window, search results & upload window & choose to show Chat. If you see someone with a smiley icon in that column, you will find it much easier to browse them rather than those who do not have chat enabled.

To give an example of how unreliable Browse Host can be: Sometimes I can browse same host, one result might give me 50 files, the next zero, the next 2,000 lol .. so it's success varies.