If your tablet is not dissolving properly this could be down to two reasons: the water isn’t hot enough or it isn’t being released from the detergent compartment at the right time.
You should first check that the cycle you are using is hot enough (around 45 to 65°C) to fully dissolve the ingredients – see your manual for more advice.
Check that the spring on the detergent dispenser door/clip is working. Sometimes they get stuck and it can mean the tablets aren’t released at the proper time, i.e. when the water is hottest. If you’ve found that this is an issue, you may want to check our articles on dishwasher maintenance and care.