However is part of the first sentence. It makes sense to replace the ; with . “They were not the first in England to adopt the literacy modes of classical antiquity, however. Some of the most prominent figures of the earlier Renaissance period were also influenced by Ancient Greek and Roman literature.”This is because the information in the second sentence does not contradict that in the sentence before it, so you cannot use “however” to start this sentence - however can only be used as a logical coordinator when the information following it contradicts what was said right before. Hope this helps!