Please search before posting. This has been answered many times in the last few days.
The latest Microsoft Windows update (KB4093112) has caused an issue with tablets and Photoshop.
You can either - undo the update
Do the following :
1. Use notepad to create a text file and type in :
2. Save the file as PSUserConfig.txt in the following location C: > Users > Username > AppData > Roaming > Adobe > Adobe Photoshop CC 2018 > Adobe Photoshop CC 2018 Settings
3. Go to the tablet properties and uncheck "Use Windows Ink"
4. Restart Photoshop
That is it - all should now work well (you need to do all the above steps to retain pen pressure)
There is a third option if the above does not work on your tablet. Microsoft made this change intentionally and they have issued a way round it with registry change (see link below). However for Photoshop and most tablets the PSUserConfig method works.