Flows not working - Troubleshoot checklist

[SangeetaMishr]

Add more steps here which have be needed to check when flow isn't working for a user

https://glific.github.io/docs/docs/Product%20Features/Flows/Others/Flows%20not%20working%20-%20Troubleshoot%20checklist/

[SangeetaMishr]

#573 this is done here hence it's duplicate issue hence closing it here.