Try going to phpMyadmin and dump this lines into database
INSERT INTO `yourprefix_group_permission` (`gperm_id`, `gperm_groupid`, `gperm_itemid`, `gperm_modid`, `gperm_name`) VALUES
(1, 1, 1, 1, 'module_admin'),
(2, 1, 1, 1, 'module_read'),
(5, 1, 1, 1, 'system_admin'),
(6, 1, 2, 1, 'system_admin'),
(7, 1, 3, 1, 'system_admin'),
(8, 1, 4, 1, 'system_admin'),
(9, 1, 5, 1, 'system_admin'),
(10, 1, 6, 1, 'system_admin'),
(11, 1, 7, 1, 'system_admin'),
(12, 1, 8, 1, 'system_admin'),
(13, 1, 9, 1, 'system_admin'),
(14, 1, 10, 1, 'system_admin'),
(15, 1, 11, 1, 'system_admin'),
(16, 1, 12, 1, 'system_admin'),
(17, 1, 13, 1, 'system_admin'),
(18, 1, 14, 1, 'system_admin'),
(19, 1, 15, 1, 'system_admin');
Don't forget to change 'yourprefix' to the correct prefix.
This are the default values for a XOOPS 2.3 installation so, if they were deleted, you will be able to insert them again.
Perhaps is better if you have a look first to see what values were deleted, and the insert the missing ones.