Hi it was 3 month to begin with. I thought this would be the case. I just feels it's unfair. This person has already went through 3 finance assistant who all kept leaving. It's making me feel that I'm incapable but I think I know that it's just the way I've been treated

Hi I am looking for a bit of advice. 3 months ago I got a job as finance manager in a charity. In the first few weeks everything was fine. I was asked to try to bring everything up to speed as their previous finance was off sick and eventually retired. This involved year end processes, 1st qtr accounts and into the 2nd qtr accounts. There's a finance officer who's worked there for 18 years and I asked her Time and time again to show me how things worked but she didn't. I eventually said to a senior member and she said this person is notorious for being like this especially to junior staff. Another senior then wanted to meet with me and she that I was being bullied. Both of these members didn't want me to leave. My senior was on holiday when all this came about. So after he came back, the other senior members told him what had happened. I explained that I am find it difficult to work her as I am getting nowhere and she wasn't showing me how to do things she was just pointing to files etc. He said that she has to show what to do so I tried again but unsuccessful. I then went on holiday and just returned today only to be told that this isn't working out. I had no previous verbal or written warnings or nothing to suggest this was going to happen. I think something has been said against me during my time off and he taken her word against mine. I feel as though I have tried to do everything I could. Would anyone know if I have any comeback please?