Lg tv 42ld550 stays on standby and can not be switch on

we've no idea at all what system you have or where you are or all equipment names and models there.
The word Gateway here, means Gateway computer company.
my guess you confused that? so i moved you to LG.
but really this is router issue, to connect.

how far is TV from your router 10feet or 100feet or?

i guess that LG 42LD550 is TV and you posted a TV question to computers? LG is not Gateway ever.
to connect wifi from the TV to your router
takes knowing the credentials of the router wifi channels.
SSID
WPA/WPA2
and paraphrase.
is it your router,or does the ISP own it and is locked out.

there are 3 ways to connect, the above
WPS, if it works at all and a feature of your router.
wired, ethernet cable end to end (the easy way)

wps has time out delay, so you need to push the button then go to TV quickly and try to connect.
this button on mine is turned off, for security.so....

https://www.screenpush.com/wps-button-on-router-and-its-functions/

Those blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices.
https://homenol.blogspot.com/
https://electronicshelponline.blogspot.com/
If blinks continue without any pause, or the LED light stationery; the main board is faulty.
Search the site by type in the "brand name" to your device; [Exclude the model number], in the "Search box at the top right of the display window of the Homepage" to get gathered related posts. See the site by a desktop. Mobile view has no search box. If you are viewing it by your mobile, see it in webview/

To use a USB flash drive with the LG 42LD550, the drive must be formatted as a FAT32 or NTFS device. The drive should be 32GB or less. Not all USB devices will be recognized - this can be a driver issue. (I've had a few devices that didn't take a USB flash drive, if the drive required a driver to run under Windows 98.) If you use an external drive (portable or desktop), keep the drive capacity to 1 TB or less.

Next what files are on the drive? This TV will only recognize JPG images, HD DivX (.avi and .divx) movies and MP3 audio files. The not all codecs may be supported with these formats. Some people report losing the ability to play movies after certain firmware updates. If the drive has too many folders or files in a folder, it may not work. (This will happen sooner with the FAT32 format.) See page 96 of the user manual to see the file format limits on the USB port. The manual is available on the TV support page: https://www.lg.com/us/support-product/lg-42LD550 . The current link to the manual is http://gscs-b2c.lge.com/downloadFile?fileId=oqXZ71Wn8YXJ3OKzy9leAw .

I hope this helps.

Cindy Wells

LG 42LD550 LCD TV problems

here is a video that might help. i would also look for bad caps on that board

Fault with its main board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. http://electronicshelponline.blogspot.com/ . In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

http://www.lg.com/us/tvs/lg-42LD550-lcd-tv Read the specs. You'll need the adapter which is sold seperately.

hi have you tried factory reset if this don't work you may have to go into service menu and reset the tv back to when you first brought it, to do this, there's 2 sequences you have to do 1 press hold menu on the remote and menu on the tv for about 10 second , if this don't work try this one, press and hold ok on the remote and ok on the tv for about 10 seconds you see a menu pop up scroll to reset but you have to retune the tv in again hope it helps
regards
shaun

First thing that comes to mind is to have the power supply capacitors checked for any bulging. Outside of that, you could have a defective main board or power supply board. Unless you have electronics repair experience, you will need to get the set diagnosed.

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After the network is connected to the TV, you have to go into the TV’s network menu to complete the setup process.
If you look in your owner’s manual starting on page #55-#57, you can read the direction to walk you through the wired network setup process.
It should be very easy to setup as long as your router has the DHCP turned on. That allows the TV to automatically assign it an IP address on your network.
If the DHCP is not turned on in your router, then the TV’s IP will have to manually entered by you.