There are several possible things why this message appears:
1. the file na,e is misspelled, therefore file cannot be found.
2. the file had already been deleted.
3. The sup had just been converted to Native IOS and the file was put in the bootflash: while it was in hybrid, this will result in the native not being able to find anything in the bootflash as it was copied there in a hybrid format that the native is now not seeing.
Try to see if the file still exists with "dir sup-bootflash:", if you see the file, make sure it does not have "D" on it which woudl mean it's maked for deletion but it has not freed up the space.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...