Lost Https Access

Hi 

Am facing a strange issue where when I uploaded the backupconfig of the firewall we lost https or http access to the firewall I will explain everything below (I did a session with forti support but the result was you shouldn't take back up config from 7.6.0 version to 7.2.10 version tbh I wouldn't say this is true at some point but I will try my lost hope here)

So we have a fortigate firewall that is on 7.6.0 we wanna role back because this version is seriously bad I toke the passive firewall factory reset it also rolled back to 7.2.10 then toke the back up config from 7.6.0 and uploaded it in the 7.2.10 suddenly no https \ http access I will write everything down that I tried : 
1-interface up allow access ping https http ssh(i can ssh into the firewall)

2-change the https port to default 

3-no local in policy is configured

4-trust host is configured I added the whole subnet of my vlan (me and the firewall are on the same vlan)

5-diagnose sniffer to see what is being blocked when i try https there something wrong with the tcp connection I will list below the log

1.873909 172.20.0.31.59812 -> 172.20.0.56.443: syn 3386744634
1.874091 172.20.0.56.443 -> 172.20.0.31.59812: rst 0 ack 3386744635

after many search it turns out there is issue with the tcp connection but I still couldn't understand why am not getting https access could anyone help me here? 


many thanks in advance.