Boot (tailgate) stays locked - what can I do?

I have a Skoda Fabia - station wagon (2006) 1.4 TDI. Last week I noticed that I began to have problems the boot - using the rubber push handle. If I lock the car (using key fob) - then re-open manually - with keys - in door, sometimes the boot may open - but today it seems permanently locked! Any solutions? Is it possible the Fob key may need a new battery? - or the car battery is also too old? A faulty relay or used fuse? Or the mechanism itself? Any suggestions welcome