can't place a new base on server since last update

There are a number of situations which can prevent the placing of new bases.
As @tjapka has said, the number of RP & credits needed to allow the research is the first hurdle. You need to research the new base.
If you have the researched the new base but it is greyed out despite having researched the base, then you need to check that your CY's are all fully restored.
If the button is available then you need to be in an area where you can place the base.

Screen shots would be of help here, one of the area listing your bases on the right of the screen and another when you try to place it showing where you had hoped to place it.

Generally you get a tooltip message telling you why you can't place a base when attempting to do so after researching it.