The problem is probably that there just happens not to be anyone who wants to sell their shares on the open market at that price. I think this is a thinly-traded stock, i.e. there are relatively few buyers and sellers in the market for these shares. Looking at the London Stock Exchange website (https://www.londonstockexchange.com/stock/BRH/braveheart-investment-group-plc/trade-recap) just now, the last five trades have all been ‘off-book’ trades, meaning deals made directly between two parties rather than through the exchange. The prices of those trades are reported to the stock exchange (prices ranging from 89.13 to 89.95), which sets the ‘market price’, but the parties transacted directly with each other and it doesn’t necessarily mean that they would have been willing to sell to you at the same price.
If you really want to buy, you may have to adjust your price to attract a seller. Market makers will buy and sell almost anything as long as the price is right, but there is never a guarantee that someone will sell their shares to you at the last known transaction price.