What Causes The Issue? 

This problem is most commonly caused by having a bid that is smaller than the minimum floor price (the lowest amount you can bid) in the publisher.

For example:

• The bid amount of a keyword, ad group, or product group is less than the minimum bid.
• Your platform account is set to USD. Microsoft Advertising has a minimum floor price of $0.05 for Search Bids and $0.10 for Content Bids.
• Your Microsoft Advertising account is set to GBP. Microsoft Advertising has a minimum floor price of £0.05 for both Search and Content Bids.
  Automated bidding is careful to bid more than $0.05 if your Marin client account is set to USD, however, since the Microsoft Advertising account is GBP, this bid is still not greater than the floor price and will get rejected by Microsoft Advertising.

See the following article for details on Publisher Requirements & Restrictions.

How To Fix The Issue 

You should set your Bid Floor rule price greater than that of the publisher. In the above example case, you might try setting your floor price to $0.08 or above to ensure bids are always above $0.05.

Search Bid and Content Bid are both mandatory fields if you are attempting to modify the keyword bid.