Solved. I moved the whole installation to my localhost. Just Host didn't offer PHP version earlier than 7.
Copying the database presented a few problems so I list them here in case anyone is interested.
When you create the database to import into also add a new user with the data found in
<frontaccounting root>/config_db.php
.
Without this you can't login and you won't be told why.
Upload file size is limited in my local php.ini, so find and edit these lines in php/php.ini.
memory_limit = -1
upload_max_filesize = -1
post_max_size = -1
Also on a local site execution time may need increasing, so find and edit phpMyAdmin/libraries/config.default.php.
$cfg['ExecTimeLimit'] = 600;
This gives you 600 seconds.
Thanks for your help.