If the project you're looking for doesn't show up on Slack or Teams, there are a few things you can do to find it.
In Slack, you can try typing the name of the project. When you're entering your work hours in Slack, the list of projects will initially load a maximum of 100 items. If you have more projects than that, including Time Off options, the rest will be loaded dynamically when you start typing.
On Microsoft Teams the card can only load 30 different projects and it doesn't allow typing, so we load the projects based on recent activity. We recommend archiving projects that are no longer active to ensure the active projects are the ones displayed, and using the Report Center to log time whenever the project or time off type doesn't show up (the project should appear in the Teams check-in list after being used in the Report Center).
These are limitations of the Slack and MS Teams platforms and there's nothing we can do to change it.
On both platforms, when you frequently log time on a project, it will be easier to find on the Recent projects separator.
If the project is still missing from the project list, you should make sure the project hasn't been archived, renamed, or deleted, and make sure the project isn't exclusive to a user group you are not a part of.