Internal Server Error in flow designer

[Royal1]

Unable to run the flow with simple activities but i am getting the 

Internal Server Error 
initially i didn't get this error , not sure what is the reason , Please help on it 

[Hemanth M1]

Hi @Royal1 , 

Will you be able to share what's your logic in the flow (This error mainly comes when it's some syntax errors like flow variables are undefined, field data types issues) 

We may need to look at your flow to understand the issue.