The apply button will legitimately be inactive/greyed out for files tat a) aren’t infected, just can’t be scanned, b) detections in memory, which aren’t physical files and c) if you have closed the initial scan, if you subsequently open the log, it is historic data and action can’t be taken. Read my Reply #2 above.

So we need more information:
File name, location, malware name, Action, Result and any other data in the report ?