Is your inventory full by any chance? This could be a possible reason why it will not allow you to accept the items.
If this does not help then I think we will need to get our Customer Support team to look into this for you. I would suggest to log a ticket regarding this through the in-game portal.
Please make sure to give a clear description of the issue you are having so that one of our in-game agents can help.
how do I do it?