On the packet capture, here's some samples...
xxx.xxx.xx. is the destination IP the vpn client is attempting to connect to...
xxx.xxx.xx.198.1935: Flags [SEW], seq 2856775745, win 65535, options [mss 1460,nop,wscale 6,nop,nop,TS val 489566124 ecr 0,sackOK,eol], length 0
xxx.xxx.xx.198.1935: Flags [.], ack 1, win 65535, options [nop,nop,TS val 489566145 ecr 1006200408], length 0
next line is:
xxx.xxx.xx.198.1935: Flags [P.], seq 1:235, ack 1, win 65535, options [nop,nop,TS val 489566146 ecr 1006200408], length 234
later there's
xxx.xxx.xx.163.443: Flags [SEW], seq 969374625, win 65535, options [mss 1460,nop,wscale 6,nop,nop,TS val 489566268 ecr 0,sackOK,eol], length 0
Again, vpn connects from ipad without issue on other wifi networks. In theory, it could be the cable modem but that has no firewall, dhcp, etc.