I tried to reset MySejahtera Password on my iPhone and hit this issue. The error message was "There was an issue loading your page which may be due to unstable network connection or high traffic volume on the system". I'm very sure my phone was able to go on the Internet as sites like google and bloomberg were accessible.
MySejahtera app is such an integral app nowadays for every Malaysians and foreigners living in Malaysia. Without the app, you can't really go anywhere as all places require MySejahtera sign in for Covid19 contact tracing. I think if MySejahtera system does down one day, there will be big havoc around.
MySejahtera does not have a helpdesk email or phone number. All support issues are logged via their Helpdesk website. This site can be access via normal desktop/laptop web browser. In MySejahtera also this site can be access but if MySejahtera is not accessible, then need to use the desktop/laptop web browser.
πLinks
https://mysejahtera.malaysia.gov.my/