Recommended solution

Since there have been some users who encounters this issue. We have implemented something else.
So, just update/upgrade to v 2.6.0.

Previous solutions

May I know what version did you use before upgrading to v 2.5.9 and how you perform the update?
If you upgrade the plugin by uploading the plugin files manually via FTP or something similar, make sure to deactivate and activate the plugin again.
If you don't do this, the installer/upgrader script won't be invoked/run.

If possible, can you check your database and see whether all of these tables are exits?

• wp_xmt_acc
• wp_xmt_ath
• wp_xmt_twt

If you find any or some of them are missing, it must be that, somehow, the installer script is not called/invoked/run.

FYI, in the previous version, there is only one table used by this plugin which is wp_xmt. In this version, that table has been renamed to wp_xmt_acc and there are two new tables.
You cannot find/see your profiles mostly because of that, somehow, the installer script failed to rename wp_xmt to wp_xmt_acc.

To fix your issue, there are two methods.

First method, download the attached xhanch-my-twitter.zip (below) and extract it. You should find xhanch-my-twitter.php
Then, upload xhanch-my-twitter.php to overwrite the existing wp-content/plugins/xhanch-my-twitter/xhanch-my-twitter.php on your server

Second method, run these SQL queries manually via PHPMyAdmin

create table if not exists wp_xmt_twt(
id int(11) not null auto_increment,
acc_nme varchar(100) not null,
twt_id bigint(20) not null,
twt_ath varchar(100) not null,
twt varchar(255) not null,
twt_dtp varchar(19) not null,
twt_typ varchar(3) not null,
twt_src varchar(255) not null,
primary key (id)
);

create table if not exists wp_xmt_ath(
id int(11) not null auto_increment,
uid varchar(100) not null,
nme varchar(100) not null,
img_url varchar(250) not null,
dte_upd bigint(20) not null,
primary key (id)
);

alter table wp_xmt
add las_twt_imp_dtp bigint(20) not null after prf_cch_dtp;

rename table wp_xmt 
to wp_xmt_acc;

Note: replace wp_ with your table prefix

Just did the same thing and upgraded from the latest version to 2.5.9 and all the profiles are gone. Upgraded through wordpress and then tried to fix it with importing old profiles and fix issues on the my twitter page and nothing. Basically says it can't find the database.

Just did the same thing and upgraded from the latest version to 2.5.9 and all the profiles are gone. Upgraded through wordpress and then tried to fix it with importing old profiles and fix issues on the my twitter page and nothing. Basically says it can't find the database.

How about my solution above?

Got the same problems. But your solution works. Thanks.
Why did this happen ?

Got the same problems. But your solution works. Thanks.
Why did this happen ?

Which one do you use? The firs method or the second one?
I've stated the cause above. The cause is actually: somehow, the installer script is not called/invoked/run.
The reason of why the installer script is not called/invoked/run remains mystery.
I perform this update successfully to all my WordPress websites so I didn't expect some of the plugins users eccounter such issue.

Which one do you use? The firs method or the second one?

the second one, the SQL queries.  There were missing tables and wp_xmt didn't change to wp_xmt_acc.
I didn't try the first one.

Making the SQL fix did not work, nor did trying to update to the lastest version - in fact, the mere presence of your addon sends my site into a 500 Internal Server Error, which only disappears when I remove the addon.  So, unfortunately, I will no longer be using your addon.