Site-to-Site VPN to Juniper

I am trying to create a IPSEC VPN from our Fortigate to a Juniper.

On the Fortigate side I have no access to CLI as managed by a third party. I have asked them to look into it but response may be slow.

On the Juniper side, it is again managed by a third party and I have no access.

We have matching algorithms etc and this is the output from the Juniper:

set security ike proposal IKE-PROP1 authentication-method pre-shared-keys

set security ike proposal IKE-PROP1 dh-group group5

set security ike proposal IKE-PROP1 authentication-algorithm sha1

set security ike proposal IKE-PROP1 encryption-algorithm 3des-cbc

set security ike proposal IKE-PROP1 lifetime-seconds 86400

However the tunnel does not come up. The only logs I can see in the Fortigate GUI constantly repeats:

 08:16:49 negotiate    success     progress     IPsec phase 1

but it never passes Stage 1 of P1.

Any suggesting why we are not getting past Stage 1 P1?