Hi Himanshu,
SDM uses encrypted administrator credentials stored which are stored secure store to use deploy service.
If you have changed the password, updated in secure store and is correct, the you should be able to logon to VA.
If not, then
Goto /usr/sap/SID/DVEMBGSXX/SDM/program/config and open sdmrepository.sdc file to see the values of SecStore.properties and SecStore.Key are pointing to correct path. You can verify this from configtool or config.properties in configtool folder.
If you are not able to save this password in configtool, then refer 1228507 - Config Tool does not properly save password in Secure Store
Regards,
Divyanshu