Hello @Alon and welcome to the Community!
If you are an admin, go to the project settings of the Project (Jira Administration > Projects > [Your Project] Triple dot menu > Project Settings) and check the permission scheme. It's possible that you are not a part of the group or the project role associated with the "Browse Projects" permission.
This happens to me every now and then and this is what it usually has been.
Hope this helps!
UPDATE: It's a wrap for our first community AMA on Jira Work Management. Thanks to everyone for taking part and sharing. Feel free to keep the discussion going! Share your questions now Hi...