Is it a vintage cartridge of Sapphire?
It must be the Berry Glitch.
cases of the Berry Glitch will become quite widespread. As a result, here's the full info on the glitch and how to fix it.
What is the Berry Glitch?
The Berry Glitch is the nickname for a glitch in the coding of Pokemon Ruby/Sapphire that basically stops the game's day counter moving.(A reason to why your Umbreon didn't show up..) This stops time-based events such as berries growing, the Lilycove Dept Store's sale, and trainer re-battles from happening ( It can be fixed relatively easily, but unfixed it can seriously hinder your enjoyment of the game. It usually only appears on a cartridge that is exactly one year old, but it has been known to appear on newer cartridges for some reason.
The following are all signs that your cart has contracted the berry glitch:
Trainers stop wanting to re-battle
Berries stop growing
Lilycove Dept Store never has any sales
Game Corner never has any service days
The Energy Guru never sells vitamins cheap
The tide in Shoal Cave never changes
The Return/Frustration man in Pacifidlog stops giving out TMs
All of the recent Pokemon titles have the glitch fix installed into them. There are several different methods of fixing the glitch, depending on the game you intend to fix the glitch with.
If you are fixing the glitch with Pokemon Colloseum, Pokemon Box, or Pokemon Channel (all for Nintendo GameCube) then connect your GBA (containing the glitched cart) to the GC with a GBA/GCN link cable. Go to one of the pokemon uploading options and turn your GBA on. When the GC registers the GBA as being there it will automatically fix the berry glitch.
If you are fixing the glitch with Pokemon FireRed/LeafGreen (due out September 2004) link one GBA with a Fr/Lg cartridge to another with your infected Ru/Sa cart. Ensure the RuSa GBA is not turned on. Turn on FrLg and at the title screen, press Select and B. Also ensure that the FrLg GBA has the player one end of the link cable (the purple end of an official cable). Then press A to confirm the action. When the RuSa GBA reaches the Game Boy screen, press Start and Select straight away. The FrLg cart will detect this and begin fixing the glitch.
It is also worth noting that some games stores (notably the US Target chain) will fix your cartridge for free. All you have to do is take in your GBA and hand it over to someone working there and they will fix it for you. Hope Umbreon comes to you soon!