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If the touchscreen doesn't work, you cannot do a factory reset - is that correct?
How did you update it? is there any chance that you applied an update file for the wrong model #? which would cause damage to functions which might include touchscreen function being lost... but there is also the possible cause, that the touchscreen simply chose this time to fail, by sheer chance.
How old is your Garmin 510 ?
Then it is out of warranty at any rate. But 2 years is rather soon for a failure.
Try using the blunt end of a ballpoint pen with the pen retracted, to get the factory reset to execute.
Then just touch with the ballpoint on the X, to cancel the factory reset, right?
That's the beginning of initial setup - possibly, after a factory reset.
Select your language... unless the touch-screen won't work. (Try a pen too, of course.)
Then your device's touchscreen has failed, and it will have to be repaired at your cost, or else replaced... the warranty is long expired, so unfortunately that's all there is to it.
For Garmin 510 ... Garmin charges $ 79 for repair to an Edge 510 that is out of warranty.
Another source of repairs can be inquired into, at
which has a blue square at the left to click on to request a repair quote.