What is the most common cause of a white screen error in a WP theme?

Question

Programming

We developed a WP theme for a client on our hosting and everything was fine until we transferred it to the client's host. At first it turned out that it was absolutely not configured, after not a long setup, instead of a site, I got a white screen. Disabled plugins, didn't help. After disabling my theme, surprisingly WP worked. Other standard themes work fine (didn't test more complex ones), ours causes a white screen (although everything is ok on other hosts where we host).
Where to start digging? Where can such problems occur more often in the topic? What can cause problems with the theme in hosting?
It would be more logical to refuse this hosting, but the client insists. The client cannot refuse hosting, as he rents a domain and a host, and of course they do not want to give him a domain.
log gives no errors.

Answer 1

Rating of the most common errors during deployment:
- Disabled short_open_tags directive
- PHP version does not match (use of short array notation when hosting is still php5.3, and other joys of life).
Treated by viewing logs.

Answer 2

:) most often the absence of a semicolon at the end of the line ;) But seriously, turn on error
logging or WP debugging mode .. well, or something similar in Google for these keywords.