Thanks for that information and sorry for any delay.
Without the model it will be hard to be precise, but I will tell you some things that are common in these cases.
First, almost all of these devices comes with a "charging dock" or clip, and often over several months of non-use, the contacts of that dock can become a bit "stiff" OR get some dust or dirt on the contacts themselves.
The same is true (dust/dirt/grime) of the charging contacts of the watch itself.
So the first thing I would do is CLEAN both sets of contacts - with a little bit of alcohol and a lint-free cloth, or a Q-tip. And make sure the dock contacts have a good amount of "spring" in the, and move freely.
Then I would place the watch on the charger dock and let it charge for AT LEAST 3-4 hours - before expecting any response. But often after about 20 minutes or so, you MAY see the "charging indicator" appear on the screen, which will let you know it is starting to take a charge. If that happens, leave it on the charger until full is indicated, then remove it and give it a TEST. This is because the former satellite "lock" will need to be found again (happens after a few weeks of non-use).
Please give that a try when you can, and let me know what happens.
And when you have the model of the device, let me know what that is and we can take more steps - if needed.
Take Care, Greg A.