I feel there is still hope for your plant. Just repot once more in a well draining media, use shallower, smaller container. Give a couple of days then water the media thoroughly. Allow time to dry out.
Patience will be your friend. Summer is typical active growing time for them but they adjust slow as it heals the roots/produce new roots to anchor and absorb moisture at root zone level.
Always remember cacti are drought tolerant but like any living plant it needs its fair share of water during the active growing period.
