I had the same issue with installing NW 7.50 (on IBM i)
I resolved it by completing the defualt profile
/usr/sap/GWD/SYS/profile/DEFAULT.PFL
SAPDBHOST =
was completed by me to
SAPDBHOST = <DB Host>
I also had to adjust to the following:
| rdisp/mshost = SAPDEV04 | |
| rdisp/msserv = sapmsGWD |
rdisp/msserv_internal = 3948