Sometimes adjusting the file transfer timeout facilitates Send-and-Receive in the Web Assistant. Adjust that via the Settings button. The setting that works for any individual varies so that testing different settings is the only way to find one that works. The default is 180 seconds. Oddly, sometimes setting it shorter works better but other times setting it longer works.
Assistants | Web Assistant | Settings button | File Transfer Timeout | type a number or click the up/down arrows