The warning is that the number is red =) But it is still possible to send the ship regardless if its full or not. If its literally impossible to send it i could be that you dont have enough sailors to send it , did u check?
If your sailor count is ok then it should be possible. I have 43 ships and since there are so many I often click super fast and sometimes I miss the red number and still send the ship.. doesnt really matter since itll be back in 30 mins...
Keep me posted !
ps. : Yes they do read the posts , but given the high number of them they cant reply to all of them (which is why Im here) but if we cant fix this ill forward it to them 😉