Adding a new layer of shower grout filler is a relatively simple process, but you have to be careful. A small gap or hole can turn into a major issue, and may require professional help. This is because water under the tile can cause the mortar to break down, leaving you with a completely ruined shower.
Instead of attempting to repair it yourself, call a professional to take care of the job. Investing in a new shower grout filler can help you avoid major repairs down the road.