weak achilles?

One of my achilles is extremely weak - I went to the physio this morning and she did the Thompson Test and its not torn, however I can’t rise to my tip toes on that leg - so what's going on?
This was preceded by a couple of weeks of a sore achilles which I (stupidly) ran through, crunchy creaky crepitus and all, now it doesn't hurt at all but is extremely weak and floppy feeling? what's going on?
I'm hesitant to walk on it let alone run, but am training for a half marathon and was really building up to my intense training period and want to figure out what this is ASAP - any advice would be appreciated thanks