Plumbing - cold tap in kitchen sink not working

Hi there. I have a one bedroom flat with tenants. The kitchen sink cold tap is not working (apparently it’s been slowly not working for a few weeks, and now is not working at all). The hot tap is working with good pressure. The washing machine, next to the kitchen sink at the same time has also just stopped working. The bathroom cold and hot taps are working fine, as is the heating. There are no problems in the rest of the building. We had a previous problem in 2022 when the washing machine stopped working because the washing machine drain pipe was blocked from debris being put down the sink. I wonder if this is an issue with the cold supply pipe to the sink and washing machine related to a blockage or maybe a valve problem. I’d be grateful for any help here. The tenants will be in the flat on the morning of Thursday 19th November.