Finally found there is a error.log which says:
Feb 26 2022 14:33:34
{“type”:1,”message”:”Out of memory (allocated 700448768) (tried to allocate 1048576 bytes)”,”file”:”\/homepages\/27\/d843729081\/htdocs\/clickandbuilds\/WordPress\/MyCMS2\/wp-content\/plugins\/all-in-one-wp-migration\/lib\/vendor\/servmask\/database\/class-ai1wm-database-mysqli.php”,”line”:63}
How do I fix this issue?
Thanks in advance