E5 is related to water supply in the documented Toshiba AW-E900LM. The valve, water availability, and inlet restrictions are the first external checks.
Page 18 of the official AW-E900LM manual confirms that path. Its flow rates and times do not set limits for other Toshiba models.
If no water is entering
Check that the valve is open and that there is no outage. If the unit was in a freezing environment, do not force a rigid hose if it has frozen, and do not apply flame or boiling water; follow the recovery steps in its manual.
Check whether the hose is crushed. The inlet mesh or filter should only be inspected using the user procedure, with the water turned off and the power disconnected before the indicated intervention.
On the AW-E900LM, once the condition has been corrected and the drum is stopped, the manual says to open and close the lid and press Start/Hold. If E5 returns with water supply available, report whether little water or no water enters and request service. Do not assume the alert is due to pressure or the inlet solenoid valve without checking it.
If your Toshiba model number is different, first confirm the chart: sharing E5 does not guarantee the same fill logic.