Wireless computers -- from simple to GPS types that can sync to mobile devices -- can be a bit finicky to set up.

As other folks noted, some LED lights can interfere with wireless connectivity. Moving the headlight or computer a few inches apart usually helps.

Some low end basic wireless computers have very limited range. I have one that can reliably transmit only 18"-24", so the sensor must be on the front wheel only if the receiver is on the handlebar or stem. No-go if I want to use it on the rear wheel for indoor trainer sessions, unless I move the sensor/display unit to the top tube closer to the saddle, or set it on a table next to the bike/trainer setup. That's the main reason I finally stopped using my first wireless bike computer.

Since then I've used a 2012 era Wahoo kit that converted my iPhone 4s to an ANT+ receiver, with magnet based speed/cadence sensors mounted on the chain stay to pick up magnets on the wheel and crank. That's great for indoor trainer sessions, but too bulky for everyday rides. The battery drained after only an hour or so outdoors with the display on. The magnet type sensors were generally reliable but there were a few areas with radio frequency interference that caused some screwy data.

Now I'm using a low priced but pretty good XOSS G+ GPS computer that syncs to Strava after rides. It's pretty basic but does what I need. It's compatible with my Bluetooth and ANT+ devices. The earth induction type speed/cadence sensor has spiky data more often than the magnet type sensors, but it's not bad.

If I was concerned about accuracy for short segments or some sort of contest, I might go back to wired computers. But all of my wireless setups have been accurate enough for my purposes. There's hardly any difference between data from my phone using GPS only, compared with magnet based ANT+ and earth induction Bluetooth sensors. The minor discrepancies in average speed, distance, time, etc., aren't worth worrying about since I'm rarely in contention for a KOM where one or two seconds might matter. On my best day I'm 2-3 seconds behind the top ten on short sprint zones, and a full minute or more behind the KOM on favorite 5-6 mile time trial segments.