Regarding occurrences when LED signs require maintenance, there are two different scenarios: A missed application or a missed installation.
On the application side, UL has guidelines regarding the use of specifically-rated products.
So, for example, you should not use a damp-rated product in a wet-rated application. It will likely fail. Also, one should ensure the wiring aligns with the standards required for the application. For example, when installing in a wet-rated environment, one should use electrical grade RTV (room temperature vulcanizing) silicone to seal the wire nuts when making the connection.
On the installation side, there are a couple of things that can go wrong. For example, the wiring may not be properly connected, or the power supply may be installed incorrectly.
One of the common errors we see is the power supply placed in an enclosure that is not to code, mounted close together in a non-ventilated space. UL specifies how to install power supplies in terms of clearance from one another, etc. If they get crammed together, they can overheat.
Those are the more common installation errors. Usually, the LEDs are fine, but they’ll go out because the power supply has failed.