I’ve been a big fan of Coda the last few years of using it (for non-version controlled projects, having a version of Transmit built into the software has come good time and again). The one rare, problem I’ve picked up using it is it can struggle with projects connecting over SSH, without much documentation for a workaround.
I spent ages sure my fingers must be failing me rather than the tech, mixing and messing with login details until I eventually discovered that you can supersede the settings that are entered in the project bookmark by adding a config file into the .ssh folder with details to match it. After adding that, a quick reboot of the software and Coda should pick it up automatically.
Documented gist of what exactly should match up is below, and a comment-free version (as it should be in the .ssh folder) below that.