Hi! How large are your individual texts in the data? And are you loading from a format that can be read line by line (e.g. JSONL) or a format that needs to be parsed and loaded into memory upfront (e.g. JSON)?
"No tasks available" is shown if Prodigy comes across an empty batch and typically happens when there's nothing more to annotate. If there is more data, this could indicate that the server somehow takes too long to produce a new batch and/or some race conditon causes an empty batch to be sent before the next one 
The easiest workaround should be to just make Prodigy try again and send the next batch, either be refreshing your browser or by restarting the server (which should let you start right where you left off because Prodigy will skip all questions that are already annotated in the dataset).