The migrated piece is an upgraded version ?
What php version is running?.
Is the link for your site (suppose is same as old one) also changed by IP? (in site preferences maybe a fixed domain name in use?).
Updating/-grading 0.7 to v2 is best done (not live but on pc locally) in steps ?>
0.7 > 1.0.4 > v2 (ex 2.1.9) (thus check outcome IN EACH version, before moving on), BUT you could end up in php circumstances that some parts of your old site use too old pieces of code, that interfere with the present php coding..(Going over php 5.3.6 with 0.7 xx ; some v1 versions could indicate such (specially plugins).
please keep in mind that the first 0.7 version is dated 2006, and we are on the verge of 2018/19 so there are many changes (in php, sql, coding etc...)
Maybe a url (even the old one) could shed some more insight.