Your team limit is 27, what  means you can have maximum 4 bids opened in one moment, because your current team number is 23.

Probably you try to bid more than 4 players

It happened the same to me, then i realized that i was offering for a player with age below 17 years old (15 or 16 y.o.) and i can have only 3 youths and i have (for example) one youth and i was offering for 3 youths and i was winning the auction for two of the 3 youths and i was attempting to offer for the 3th youth, then the system showed that message to me

Yes, this is related also to youths, on the same rules as adults

Here is the situation 
This is your main squad, the club has 23 players eager to show you their capabilities. The squad size limit is 27 players, limited by the stadium Dressing Room level of 1
i have 23 in squad and 3 youth that are in training not in team yet they will be 17 next season !! so i still have space in team and there is no Bid open i still get this message You have too many open bids, your squad size will be over the limit 
i cant understand please admin check it thanks and any one who can understand the situation please reply

Issue Resolved :)
I had many players short listed i removed some and that resolved the problem Ty every one who tried to help