Webadmin / Portal can't acces with proxy enable

Dear all,

I've a problem for access to webadmin or portal of my astaro when the proxy enable on browser.

My conf :
Astaro ASG 220 v8.300
HA
Astaro IP : 192.168.1.200
Astaro webadmin : 192.168.1.200:9999
Astaro portal : 192.168.1.200:8888
I used proxy distributed by astaro DHCP.

On the browser, if I enable proxy I cannot join the webadmin or portal
I can join the portal if I set the port 80 or 443 for the portal access.

In firewall log I can see this :
WebAdmin connection attempt
TCP 192.168.1.200 : 31224 → 192.168.1.200 : 9999
[SYN] len=60 ttl=64 tos=0x00 srcmac=0:0:0:0:0:0

WebAdmin connection attempt
TCP 192.168.1.200 : 43341 → 192.168.1.200 : 8888
[SYN] len=60 ttl=64 tos=0x00 srcmac=0:0:0:0:0:0

I add the port in target allowed on web filtering / advanced.

Anyone knows the answer ?

thank you for reading and for your support