First, make sure the strings is same like 'FlowType'.
Second,you can try to debug your code like below.
Session["FlowType"]="aaa";
string test = Session["FlowType"].ToString();
Check the value of 'test', is null or 'aaa'. If the value of test is correct,maybe you can print Ctrl+Alt+i to open the Immediate Window in Visual Studio. Then you can check when the Session is missing.
The last Step,maybe you can modfiy your web.config to set config about the Session.
I hope the above answers can help you.
Add Pic
![Debug in azure](https://i.stack.imgur.com/4nROi.png)
How to debug in azure. You also can google it.
step 1: Make sure publish configuration setting. Like pic bellow
![publish configuration](https://i.stack.imgur.com/knZYV.png)
step 2: When publish succeed,you can attach debugger
- My IDE is vs2019, you can click View-> Cloud Explore ,then you find you sourcegroup and web app.
- Like pic, you find it , and click, it will show Attach Debugger, then you
debugger in azure to test.
3. The first debugging will take a long time.