Hi @jet55 Are you on the £20 always on goodybag? if so, have you used up the first 9GB of mobile data? The £20 always on goodybag is designed to give you 9GB of UK data at full 4G speeds and once you used up the 9GB then you will continue to get unlimited data allowance at a reduced speed (384KB) from 8am to midnight. From midnight to 7.59am you have an unlimited data allowance at full speed.
However, if you haven't used up the first 9GB of data or if your not on the £20 always on goodybag check to see if there are any network outages in the area you are in: https://giffgaff.com/coverage-and-service
If the network is fine then try turning your phone off, waiting 5 mins and turn it back on,