I had a similar problem with a different board
I soon found that the file that uploaded was incomplete e.g. 11.8 mb file uploads but the file once uploaded was only say 7mb
Get a copy of the file from the MikroTik website under downloads, drag and drop into the file folder once it's uploaded check it's file size, if it's same size as one that you downloaded do a system reboot
Might take a while to reboot as it's upgrading, once up it should have done it
Also when it's done it don't forget to go into system routerboard and click upgrade as it updates that too
Hope this helps!
Kev