There are two online systems - Danish QSAR Database and Danish QSAR Models.
The Danish QSAR Database (http://qsar.food.dtu.dk) is a collection of pre-calculated predictions for 650,000 chemical structures. If the user's structure is among these 650,000, predictions can be retrieved, otherwise there will be no result - the system is not designed to generate predictions. The Danish QSAR Models website (https://qsarmodels.food.dtu.dk) can generate predictions for any user-defined structure, provided it is chemically correct and the software can understand it.
The QSAR Toolbox retrieves data from the Danish (Q)SAR Database and is not related to the Danish QSAR Models. The structure with SMILES CCCCCOP(=O)(OC)OCCCC is not found in the Danish QSAR Database, therefore Toolbox correctly reports that there is no prediction.