I think they stopped providing it because it has issues for many things in Manjaro if I recall correctly. May find more info in the Search. //EDIT: here is the Stable announcement thread where 4.14 kernel has been removed:
This old kernel is not compatible with SystemD which is a core component of Manjaro, so that’s why.
I meant I don’t have fiber and I notice it happens a lot, especially if you increase the concurrent connection in Pacman configuration file. With only one connection it seems to happen way less.
Regardless, if you run a pacman-mirrors command or if you manually change your mirror list, you need to force refresh the package database so the list of packages you have corresponds exactly to your current mirror state. Some mirror do not update at same time.
Most importantly is to consult the announcement thread as I said, because as seen a kernel can be LTS, but not be available in Manjaro, so the good place to know about kernels in Manjaro is the announcement thread for the branch you are using, most likely the Stable branch. Here is Stable branch threads, you can “subscribe” with the bell on top right corner and select Watching First Post so you have a notification when there is a new announcement. First post of the thread will always contain the current supported kernels, and will label kernels that will be dropped soon with the EOL tag (EOL= End Of Life) so you know when to remove them to avoid issues.
Manjaro Settings Manager should also provide an option to give a desktop notification when you use an unsupported kernel.