If you have the "Go to Arellarti" mission but things seems blocked (T'Ris never gioves green light), a common thing overlooked is to make sure everyone (including vee) has the krell uniform.
If you don't have that mission yet it will be brought by Vee (after you had sex with her, SLU5 I think) , who visits you one morning and talks of an anomaly in the Krell system. Then just follow the quest log and hints.
I recommend to have a look at the walkthrough I linked in the Main game post.