@sds Do you see an error at the time of saving ?
Expression as such works.
https://experienceleague.adobe.com/en/apps/journey-optimizer/ajo-personalization?lang=en#
Also, wouldn’t dynamic content be simpler in this case https://experienceleague.adobe.com/en/docs/journey-optimizer/using/content-management/dynamic/get-started-dynamic-content ?
Otherwise, you can have a html block on the following lines
<!--[if mso]><table cellpadding="0" cellspacing="0" border="0" width="400"><tr><td style="text-align: center;" ><v:roundrect xmlns:v="urn:schemas-microsoft-com:vml" xmlns:w="urn:schemas-microsoft-com:office:word" style="height:30pt; width:300pt; v-text-anchor:middle;" arcsize="10%" fillcolor="rgb(0, 93, 171)" strokeweight="0pt" strokecolor="rgb(0, 0, 238)"><v:stroke opacity="0" /><v:textbox inset="0,0,0,0"><center style="color:rgb(255, 255, 255); font-family:sans-serif; font-size:16px"><![endif]--> {%#if profile._firm.newslettername= "ABC" %} <a href="link1" class="arc-link" style="text-decoration:none;" data-nl-type="externalLink"> link1 text</a> {% else %} <a href="link2" class="arc-link" style="text-decoration:none;" data-nl-type="externalLink">link2 text</a> {%/if %} <!--[if mso]></center></v:textbox></v:stroke></v:roundrect></td></tr></table><![endif]-->