Vpn issue on oppo a17 android with fortinet vpn

Recently I bought a new backup phone A17 typical 4gb ram 64gb drive android phone just for work purposes.

I installed vpn fortinet as usual from play store but I noticed it disconnects whenever I minimize the vpn app. 

I struggled and downloaded the old version of the vpn app but still Im having this weird issue. I tweaked like for a day but no avail.

I didnt stop and tried again since It is a very weird issue.

Then suddenly it worked while some more configuration.

I will write here the config and hope this will help someone out there

1. There is a ram extension with this phone its like using the disk as swap, I disabled it. maybe I will turn it back on if all is ok.

2. I enabled developer options oem unlocking usb debugging verify apps over usb veryfy bytecode of debuggable apps enable absolute voplume status bar location indicator

3 battery power saving off

4 vpn permissions - manage anotification allowed on storage 

5. seems also has to do with external storage storage I replaced the memory card was a 512gb

6. private dns off 

I will just add more and try to remember