1) Put the charging case on the charge and take out the one earbud which was working.

2)  Use the earbud and check the touch function/tap is working perfectly.

3) Now put that earbud back into the charging case, and take the other one which was not working.

4) Check the earbud is getting connected and touch function is working or not.  

5) If it doesn't work, put both the earbuds inside the charging case, close the lid and again take them out and check both buds are getting connected or not.

6) You can also once reset the buds and then connect again.