GLC Hybrid Key Battery Issue

Sounds like the fob battery is the likely culprit. Have you tried replacing it? It's a fairly simple process, similar to changing a watch battery.

I haven't replaced it yet. I wanted to see if this was a common issue first. Is there a specific battery type I should be using, or a particular procedure to follow after replacing it?

It's common enough. Check your owner's manual for the correct battery type; it's usually a CR2032. While the replacement is straightforward, if the error persists or the key still doesn't work properly after the battery change, it might be best to consult a workshop. They can check for other potential issues, such as low voltage or a dead key fob.

Thanks for the advice. I replaced the battery myself; the total cost was 37€. Everything is working as expected now.